environmental impact assessment of the 2011 tohoku oki tsunami on the sendai plain abstract large areas of farmland in the sendai plain japan were inundated by the 11 march 2011 tohoku oki tsunami and covered by a discontinuous 30 0 2 cm thick sediment layer consisting of sand and or mud and generally thinning and fining inland two months after the tsunami numerous rice paddy fields and depressions remained ponded with brackish or saline water a series of field surveys in may august and october 2011 were carried out north of sendai airport in order to assess the environmental impact of the tsunami while evaporation had resulted in elevated conductivity in ponded water in may up to 68 2 ms cm 1 rainfall over the next five months led to dilution although brackish water was still recorded in depressions and on paddy fields tsunami sediments underlying soil and soil beyond the tsunami inundation limit were collected at 43 sites along and near a transect extending over 5 km inland and analysed for grain size organic content water leachable ions acid leachable metals and exchangeable metalloids water leachable anion and cation concentrations were elevated in sandy and muddy tsunami deposits and soils particularly in areas where seawater had stagnated for a longer period of time after the tsunami with up to 10 5 cl 6 6 na 2 8 so 4 440 mg kg 1 br measured in surface sediments the impact of saltwater inundation was documented in the chemistry of soils underlying tsunami sediments which were affected by salt contamination down to 15 cm depth and soils not covered by tsunami deposits the latter implies that the extent of tsunami inundation may successfully be determined using geochemical markers in absence of any sedimentological evidence water leachable ions mostly decreased over time however they remained high enough to impact on rice farming which was completely halted in 2011 although further work is required to assess the longer term impact of tsunami inundation flushing of salt with freshwater as well as the possible removal of sandy muddy sediments and underlying soil are recommended to allow crop production to resume

magnetic polarity stratigraphy of siwalik group sediments of tinau khola section in west central nepal revisited summary remanent magnetization of sandstones sampled at 127 levels sites throughout a 1710 m thick siwaliks molasse sequence exposed along the tinau khola river in nepal has been studied using thermal demagnetization the magnetic remanence consists of a secondary low temperature component of normal polarity unblocked mostly below 400 500 c close to the present day field and a high temperature characteristic remanence chrm unblocked mostly between 600 and 685 c represented by both normal and reverse polarities demagnetization behaviour and isothermal remanence acquisition indicate that the secondary component resides on goethite and maghemite magnetite whereas specular haematite carries chrm anisotropy of magnetic susceptibility data reveals primary depositional magnetic fabric as judged by oblate ellipsoids and subvertical tilt corrected minimum susceptibility axes a magnetic polarity sequence established using tilt corrected chrm directions from 124 levels reveals more details not found in the polarity stratigraphy worked out by munthe et al 1983 comparison of the sequence with a standard polarity time scale harland et al 1989 suggests a depositional time range between c 5 9 ma older than chron 3r and 11 ma younger than chron 5r 2 for the section considered according to new data the horizon of sivapithecus punjabiecus fells close to the reversal boundary at c 8 54 ma the lower age limit of the normal polarity chron 4ar 1 hence the hominoid should be regarded as of c 8 5 ma rather than 9 0 9 5 ma as suggested by munthe et al 1983

dune formation on the humid tropical sector of the north queensland coast australia several previous attempts have been made to explain the apparent poor development of coastal dunes in the humid tropics in terms of lack of wind energy failure of sand supply to the shoreline excessive climatic wetness salt crust formation on beaches and the character of tropical back beach vegetation however recent published reports indicate that coastal dune occurrences are more common in the humid tropics than was formerly thought throwing suspicion on the idea that environmental conditions militate against dune formation in these areas as a whole evidence from the humid tropical sector of the north queensland coast suggests that the poor development of dunes in this area primarily reflects poor sediment sorting in the beach and nearshore zone and low wind energy at the shoreline due to the nature of the coastal orientation and physiography in relation to the prevailing southeasterly winds these limiting factors are not unique to humid tropical climates

applications of geochemistry in tsunami research a review abstract much progress has been made since the first published studies of tsunami deposits nearly 30 years ago geochemistry is now a much more widely used proxy in tsunami research mainly due to its increasingly recognised value in the identification of historical and or prehistorical deposits at times even providing the conclusive proof when other proxies are missing or equivocal but also its significance in environmental impact assessments following recent tsunamis the rapid advance in analytical techniques has also made it a more approachable and popular method as it is now often faster and cheaper here we provide a review of the applications of geochemistry including the techniques used as well as a database of studies that used chemical proxies in their investigation of recent and old events including onshore and offshore tsunami deposits chemical signatures are often used as markers of marine inundation either as salinity indicators where they can also allow the identification of the limit of tsunami inundation or tracers of the incorporation of marine sourced carbonates their applications as indicators of source material are nevertheless expanding thereby potentially providing additional information on the hydrodynamic processes associated with tsunami inundation although they are largely site specific the effects of post depositional changes in different climatic regimes are examined with a particular emphasis on water leachable components and implications for post event recovery of coastal ecosystems we demonstrate the usefulness of chemical proxies in studies of the geological record of tsunamis extending back thousands of years suggest new approaches and discuss limitations and existing knowledge gaps

structure and evolution of the northern potwar deformed zone pakistan the northern potwar deformed zone npdz is part of the active foreland fold and thrust belt of the salt range and potwar plateau in northern pakistan about 500 km of seismic reflection profiles are integrated with surface geologic and drilling data to examine the deformation style and structure of the npdz with particular emphasis on history of deformation of the dhurnal oil field the seismic lines suggest that the overall structure of the eastern npdz is a duplex structure developed beneath a passive roof thrust the roof thrust is generated from a tipline in the miocene murree formation and the sole thrust is initiated from the same eocambrian evaporite zone that extends 80 km southward beneath the soan syncline and salt range the dhurnal oil field structure is a pop up at the southern margin of the npdz and developed beneath the passive roof thrust the passive roof thrust crops out just north of dhurnal on the steep northern limb of the soan syncline an overstep passive roof thrust sakhwal fault is interpreted west of dhurnal this fault developed due to

beach ridge plain evidence of a variable late holocene tropical cyclone climate north queensland australia abstract to date most studies of long term tropical cyclone records from beach ridge plains coral shell and sand have suggested that there has been little variation in the intensity of these events over the late holocene this study of a sand beach ridge plain in northeast queensland australia using sedimentary analysis and luminescence chronology suggests there has been considerable variation in both the intensity and frequency of tropical cyclones here since the mid holocene most of the previous beach ridge studies have been of relatively uniform elevation coral shingle shell and sand beach ridges within the plain here at rockingham bay the sediments are composed of coarse grained sand and there is considerable variation in ridge height and the number of ridges emplaced over different time intervals it may be that pure sand ridges provide a more sensitive record of variations in long term tropical cyclone climatology which in turn may contribute to a considerably improved understanding of the behaviour of this natural hazard

late miocene pleistocene evolution of india eurasia convergence partitioning between the bhutan himalaya and the shillong plateau new evidences from foreland basin deposits along the dungsam chu section eastern bhutan the shillong plateau is a unique basement cored uplift in the foreland of the eastern himalaya that accommodates part of the india eurasia convergence since the late miocene it was uplifted in the late pliocene to 1600 m potentially inducing regional climatic perturbations by orographically condensing part of the indian summer monsoon ism precipitations along its southern flank as such the eastern himalaya shillong plateau ism is suited to investigate effects of tectonics climate and erosion in a mountain range broken foreland system this study focuses on a 2200 m thick sedimentary section of the siwalik group strategically located in the lee of the shillong plateau along the dungsam chu at the front of the eastern bhutan himalaya we have performed magnetostratigraphy constrained by vitrinite reflectance and detrital apatite fission track dating combined with sedimentological and palynological analyses we show that 1 the section was deposited between 7 and 1 ma in a marginal marine deltaic transitioning into continental environment after 5 ma 2 depositional environments and paleoclimate were humid with no major change during the depositional period indicating that the orographic effect of the shillong plateau had an unexpected limited impact on the paleoclimate of the bhutanese foothills and 3 the diminution of the flexural subsidence in the basin and or of the detrital input from the range is attributable to a slowdown of the displacement rates along the main boundary thrust in eastern bhutan during the latest miocene pleistocene in response to increasing partitioning of the india eurasia convergence into the active faults bounding the shillong plateau

uplift and convergence along the himalayan frontal thrust of india along the himalayan thrust front in northwestern india terrace deposits exposed 20 to 30 m above modern stream level are interpreted to have been uplifted by displacement on the underlying himalayan frontal thrust a radiocarbon age limits the age of the terrace to 1665 215 calendar bc 3663 215 radiocarbon years before present yielding a vertical uplift rate of 6 9 1 8 mm yr in combination with published studies constraining the dip of the himalayan frontal thrust fault to about 30 in the study area the observed uplift rate equates to horizontal shortening across the himalayan frontal thrust of 11 9 3 1 mm yr and the slip rate of the himalayan frontal thrust of 13 8 3 6 mm yr this is similar to previously reported rate estimates along the himalayan arc based on displacement of older plio miocene age rocks or the much shorter records of geodesy and historical seismicity the similarity is consistent with the idea that convergence across the himalayan front has occurred at a relatively steady rate through time the seismic expression of this deformation includes several great m 8 historical earthquakes which due to lack of surface rupture during those events have been attributed to their occurrence on blind thrusts yet the occurrence of a possible fault scarp in the field area indicates that past earthquakes have been sufficiently large to rupture to the surface and produce coseismic scarps these observations suggest a potential for earthquakes along the himalayan frontal thrust larger than those observed historically

middle late miocene 10 ma formation of the main boundary thrust in the western himalaya three independent data sets from northwestern india and pakistan suggest initial displacement along 1000 km of the main boundary thrust prior to 10 ma at least 5 m y earlier than previously reported regionally extensive changes in the depositional characteristics and rates of the foreland basinfill between 11 and 9 5 ma are interpreted to reflect new hinterland loading due to the formation of the main boundary thrust sediment accumulation rates sandstone siltstone ratios and thickness and amalgamation of individual sandstone bodies all substantially increase after 11 ma in well dated stratigraphic sections from pakistan to nepal across the indo gangetic foreland basin in the himachal pradesh reentrant of northwestern india a newly discovered 8 7 ma conglomerate derived from the hanging wall of the main boundary thrust indicates that source area uplift and denudation must have occurred prior to 9 ma and probably prior to 10 ma assuming a gravelprogradationrateof3cm yr threeapatitefission trackages fromstructuresattheleadingedgeofthemainboundarythrustin the kohat region of northwest pakistan indicate that rapid cooling below 105 c1 2 m y earlier these data indicate that the main boundary thrust in the western himalaya formed synchronously along strike in the middle late miocene has a displacement rate of 10 mm yr and has a displacement history that is coeval with late displacement on the main central thrust

typhoon haiyan overwash sediments from leyte gulf coastlines show local spatial variations with hybrid storm and tsunami signatures abstract marine inundation associated with the 5 to 8 m storm surge of typhoon haiyan in 2013 left overwash sediments inland on the coastal plains of the northwestern shores of leyte gulf philippines the haiyan overwash deposit provides a modern sedimentary record of storm surge deposition from a category 5 landfalling typhoon we studied overwash sediments at two locations that experienced similar storm surge conditions but represent contrasting sedimentological regimes namely a siliciclastic coast and a mixed siliciclastic carbonate coast the contrasting local geology is significantly reflected in the differences in sediment grain size composition and sorting at the two sites the haiyan overwash sediments are predominantly sand and silt and can be traced up to 1 6 km inland extending farther beyond the previously reported

sandstone body architecture and stratigraphic trends in the middle siwalik succession of the jammu area india abstract sedimentological analysis has been carried out on the coarsening upward middle siwalik succession of the jammu area india major sandstone bodies are composed of several storeys and are tens of metres thick continuing along strike for tens of kilometers these sandstone bodies are mostly multistoried representing several channel fill events few thin sandstone bodies are single channel fill events the detailed facies architecture of three of these sandstone bodies is discussed vertical sediment variation over a 1450 m thick succession was studied to document the changes the 550 m thick upper part of the succession has a greater proportion and thicker sandbodies than the underlying 900 m of the succession this is accompanied by coarser grain size and poorer representation of fine grained deposits in the upper part of the succession as compared to lower part in general palaeocurrent trends show a gradual change from ssw in lower part to sse in upper part which may be due to a change in direction of slope the probable explanations for these up section variations are tectonic and climatic change

the siwaliks of pakistan time and faunas in a miocene terrestrial setting magnetostratigraphy provides unparalleled chronologic precision for long terrestrial sedimentary records the siwaliks of the potwar plateau northern pakistan present perhaps the best example of a sequence of well dated faunal horizons spanning most of the neogene in a single terrestrial biogeographic province temporal control on fossil localities tied to multiple paleomagnetic sections is ca 0 1 m y less given special conditions of short magnetozone duration or superpositional relationships new correlations are presented for two long sections in the lower siwaliks showing the power and the limitations of mag netostratigraphic correlation within the siwalik depositional setting correlation of potwar fossil localities to those of an east african section also dated paleomagnetically are established with fossil localities from those two biogeographic provinces shown to be coeval on a scale of 10 5 yr the composite biostratigraphy rendered by the thick well exposed well dated potwar siwalik

cretaceous palaeomagnetic results from hainan island in south china supporting the extrusion model of southeast asia abstract we report the cretaceous palaeomagnetic results from hainan island south china in hainan island we collected the early cretaceous redbeds of the lumuwan formation at eleven sites we also describe the tectonic kinematics for and around hainan island since the cretaceous deduced from our and previous palaeomagnetic results the palaeolatitude of hainan island is 25 9 n 3 4 3 2 implying that hainan island was situated about 7 north from the present position during the cretaceous the palaeopole of hainan island latitude 77 7 n longitude 162 1 e k 65 6 and a95 4 4 suggests 4 0 5 8 counterclockwise rotation and 14 1 5 5 southward translation relative to the suspected coherent part of the south china block scb since the cretaceous the rotation and translation of similar sense 18 8 7 4 and 7 8 6 9 respectively are detected in the existing palaeomagnetic result from the xinlong formation in guangxi which is situated approximately 400 km north northwest from hainan island the southward translation of both areas seems to have been due to the southeastward extrusion of dissected zones within the southwestern part of the scb in a similar pattern to the indochina block which had resulted from the indentation of india into asia this sw part seems to have slightly rotated counterclockwise because its extrusion was probably smaller in scale than the indochina block and therefore it was dragged out by the indochina block this hypothesis is supported by the existence of a northwest southeast trending fault system parallel to the red river fault

reconstruction of upper siwalik palaeoecology and palaeoclimatology using microfossil palaeocommunities upper siwalik sediments exposed in the vicinity of chandigarh have yielded microvertebrates in addition to large vertebrates invertebrates molluscs ostracods and decapods charophytes pollen and spores these assemblages derive from at least four horizons of the tatrot and pinjor formations spanning the period between v4 and 1 8 ma among the microvertebrates a diverse assemblage of micromammals including rodents insectivores and lagomorphs has been recovered from these deposits these accumulations have been found to be primarily of scatological origin the most common microfossil communities belonged to pond pond bank wooded grassland sandy plain bushland and temperate montane habitats presence of gerbil rodents such as tatera associated with lizards e g uromastyx calotes and scincid in some deposits might indicate semi arid conditions or intermittent dry periods the replacement of survival oriented cricetids by reproduction oriented murid rodents in the late miocene is indicative of inter annual seasonal variations intensification of monsoons across the mio pliocene boundary a change in the dietary habits among the murid rodents has also been observed the mid miocene nongrazers such as antemus and progonomys gave way to late miocene parapelomys and karnimata and pliocene forms dilatomys bandicota nesokia hadromys and golunda which were predominantly grazers an increase in body size among the pliocene murid rodents has been inferred from the size of their first upper molars within the pliocene across the tatrot pinjor boundary around 2 5 ma among the rodents a significant change at the generic level leading to the appearance of modern forms such as hadromys bandicota nesokia rhizomys and tatera has been observed this period v2 5 ma is marked also by a great diversification of murid species probably indicating an intensification of monsoons this interpretation is further strengthened by the occurrence of a diverse palynological assemblage reflecting alternately wet and dry conditions 7 2003 elsevier science b v all rights reserved

magnetostratigraphy of the miocene pleistocene surai khola siwaliks in west nepal summary phic age dating has been carried out on sandstones of a wellexposed continuous 5500 m thick miocene pleistocene section in the surai khola area west nepal the section is situated in the siwalik range which consists of molasse sediments from the himalaya progressive demagnetization and isothermal remanence experiments prove that haematite is the carrier of the characteristic remanent magnetization chrm throughout the entire section the final polarity sequence is based on 436 samples of which 233 have normal and 203 reverse polarity antiparallel mean directions of the normally and reversely polarized samples indicate that the chrm is of primary origin comparison of the polarity sequence with a standard polarity time scale yields a time period for the section between chron lr or chron 2r matuyama and probably chron 5ab between 1 2 myr and about 13 myr

late quaternary alluvial fans and paleosols of the kangra basin nw himalaya tectonic and paleoclimatic implications abstract the paper describes late quaternary pedosedimentary sequences of the alluvial fans from the kangra basin of nw himalayas for tectonic and paleoclimatic implications in the proximal part of the kangra basin three coalescing alluvial fans namely rait rihlu fans 65 km2 kangra fans 200 km2 and palampur fans 170 km2 from west to east evolved due to reactivation of longitudinal and transverse faults and climatic changes during the late quaternary the fans are characterised by subsidence of rait rihlu fans uplift of kangra fans and tilting of palampur fans the thick 90 m pedosedimentary sequences exposed along the rivers characterise the dominant formative processes over the fans the stream flow sediments dominate the rait rihlu fans whereas the debris flow sediments dominate the kangra and palampur fans the fan sequences are also marked by the formation of strongly developed paleosols on loess l1 l3 loess paleosols and weakly developed paleosols on fluvial deposits in response to the tectonics and climate change in nw himalayas formation of the loess in proximal and distal settings of the alluvial fans is related to the cool dry climates during the advance of glaciers in the adjoining areas at 78 ka 44 ka 30 ka and 20 ka when climate was approaching towards the last glacial maxima field characters micromorphology grain size and clay minerals of these loessic deposits suggest strong pedogenesis of the loess during a warm humid climate after the retreat of glaciers in the nw himalayan region and are likely related to marine isotope stages mis4 5 in proximal and mis2 3 in distal the loess paleosols show some degree of syndepositional pedogenesis in upper horizons and are accretionary in nature weakly expressed pedogenic features in fluvial and debris flow deposits suggest rapid sedimentation over unstable surfaces related to the reactivation of main boundary thrust mbt and other regional faults

magnetic polarity stratigraphy stochastic properties of data sampling problems and the evaluation of interpretations a statistical model has been derived which can be used either to test the interpretation of a given magnetic stratigraphy or to make time estimates from the paleomagnetic data the model is based on the presently accepted statistical properties of the earth s magnetic field and the stochastic nature of the paleomagnetic sampling process given knowledge of the number of paleomagnetic sites the distribution of the sites an estimate of the geologic time span sampled and the mean length of the magnetic polarity zones the expected success of the sampling program can be calculated and compared with its actual performance in a number of test cases the theoretical results have agreed with realized results the mean time span for polarity intervals in the late neogene has been established from existing data at 120 000 years once the mean time span for polarity intervals has been established estimates for stratigraphic time span can be made by means of the statistical model of three models studied a time uniform sampling program is the most efficient for establishing a local magnetic polarity stratigraphy the least efficient strategy is an exponential distribution of samples

the occurrence and fission track ages of late neogene and quaternary volcanic sediments siwalik group northern pakistan abstract volcanic sediments now mostly bentonites and bentonitic mudstones occur throughout the late neogene and quaternary siwalik group of northern pakistan a number of these deposits have been dated by the fission track method utilizing zircon phenocrysts from these deposits and provide the chronometric constraints upon which a paleomagnetic stratigraphy is developed for the siwalik group notable in the occurrence of these altered tuff horizons is an apparent mode in their stratigraphic development from approximately 3 0 to 1 5 m y b p which coincides with the period of activity of the dacht e nawar volcanic complex of east central afghanistan fission track ages of certain tuffs for critical areas of northern pakistan are reported herein

a 7300 year record of environmental changes in a coastal wetland moawhitu new zealand and evidence for catastrophic overwash tsunami abstract three sedimentary sequences from a coastal wetland behind a sand barrier on the west coast of d urville island new zealand were examined using a multi proxy approach including sedimentological geochemical and microfossil diatom analyses with the chronology established using radiocarbon and 210pb dating data show that a brackish lagoon started developing 7300 year ago after formation of the sand barrier in moawhitu this was followed by periods of alternating wetland encroachment and open water displaying spatial variations until a peatland was established about 1300 cal yr bp the wetland was then partially drained in the early 1900s leading to compaction of the peat near the surface a coarse layer containing gravel sand and shells with a sharp lower contact in the northern area of the wetland is attributed to an overwash about 2500 3000 yr bp most probably a tsunami generated by the rupture of a local or regional fault the high resolution continuous record obtained with xrf core scanning revealed a geochemical signature ca and s for the overwash 600 m inland in the middle area of the wetland while it was absent from the southern site 1 1 km from the shore this suggests that except at the northern end of moawhitu the sand dune acted as an effective barrier preventing any sediment from overtopping 2500 3000 yr bp with only a geochemical evidence marking the extent of seawater inundation no sedimentological or geochemical evidence could be found in the wetland for the 15th century tsunami that had destroyed almost an entire community in moawhitu as recounted in m ori oral tradition p r kau although pebbles at the surface of the dune are likely to be linked to this event thus the sand dune appears to have again acted as an effective barrier for the overwash in the 15th century however our study suggests that the area might have been impacted by more than one tsunami in the last 3000 years it also shows that a high resolution continuous xrf record can provide the evidence for short term changes catastrophic or not that did not leave any clear sedimentological signature thus providing a better insight of environmental changes in any depositional environment

reduced himalayan sediment production 8 myr ago despite an intensified monsoon uplift of the tibetan plateau about 7 8 myr ago1 2 may have been responsible3 5 for the apparent intensification of the asian monsoon 6 10 around that time increases in the oceanic 87sr 86sr ratio during the neogene period have been attributed11 12 to increased erosion from the himalayan orogen it has been suggested that the monsoonal intensification may have enhanced overall erosion rates in the region5 13 if this were the case sediment accumulation rates would have increased in the surrounding basins at this time here we present a reanalysis of stratigraphic data from the indo gangetic foreland and the bengal fan which demonstrates that both of these basins experienced a decline in sediment accumulation rates 8 myr ago thus it seems that monsoonal intensification was accompanied by a decrease in mechanical weathering this decrease could be due to reduced tectonic activity decreased himalayan glaciation or slope stabilization from dense plant cover

on the southerly extent of the antarctic circumpolar current in the southeast pacific a front at 67 s in the bellingshausen sea at 85 w is shown to be part of the antarctic circumpolar current acc and the southernmost zone of concentrated eastward transport at that longitude the front lies 6 south of the polar front at 88 w and 3 north of the continental water boundary the front is continuous to the east through drake passage where it forms a southern branch of the polar front for which reason we have named it the southern polar front data from a towed profiling ctd were able to distinguish the polar front from the southern polar front even though they were only 0 5 apart thus the width of the acc south of the polar front varied considerably about a third of the transport of the acc also lay south of the polar front with 15 sv carried by the southern polar front alone at 85 w distinguishing features of the southern polar front were a water mass boundary associated with a zone of concentrated baroclinic flow and a surface salinity minimum these features also have been found at the greenwich meridian at 53 s so the southern polar front can be traced round at least a quarter of the globe to the west of the bellingshausen sea both eltanin data and the fine resolution antarctic model show that the aac is at its narrowest at 145 w where its southern boundaries lie as far north as 56 s at this longitude the acc meets the topographic barrier of the pacific antarctic ridge to conserve potential vorticity the current is forced to make a southward loop as it crosses the ridge and the current broadens dramatically the flow remains broad until forced to sharpen by the constriction of drake passage a similar broadening of the acc is seen where it crosses the southwest indian ridge south of africa at 30 e here it remains broad until it encounters the kerguelen plateau thus the eastern boundaries of both the weddell and ross gyres are determined by where the acc crosses midocean ridges

neogene magnetic polarity stratigraphy of some fluviatile siwalik sections nepal summary the magnetostratigraphy of five new sections through the neogene siwalik group of nepal is presented rock magnetic experiments and detailed thermal demagnetization experiments prove that haematite is the carrier of a primary drm or a pdrm after stepwise thermal demagnetization of specimens from all sections directions of characteristic remanent magnetization were obtained the results show a positive reversal test and exhibit inclination errors of about 20d due to gaps in exposures and extremely variable demagnetization behaviour of the haematite bearing sediments the resulting polarity sequences are poorly defined for some parts of the sections however double sampled parts of some sections yield similar results a correlation with the surai khola section appel rosler corvinus 1991 is proposed based on rock magnetic parameters ams results from three of the sections prove the existence of primary sedimentary magnetic fabrics in these sections with systematic orientations of minimum and maximum susceptibility axes correlation with a standard polarity timescale indicates that the ages of all new sections lie within the age limits of the surai khola section

molecular and isotopic records of c4 grassland expansion in the late miocene abstract siwalik paleosol and bengal fan sediment samples were analyzed for the abundance and isotopic composition ofn alkanes in order to test for molecular evidence of the expansion of c4 grasslands on the indian subcontinent the carbon isotopic compositions of high molecular weight alkanes in both the ancient soils and sediments record a shift from low 13c values ca 30 to higher values ca 22 prior to 6 ma this shift is similar in magnitude to that recorded by paleosol carbonate and fossil teeth and is consistent with a relatively rapid transition from dominantly c3 vegetation to an ecosystem dominated by c4 plants typical of semi arid grasslands the n alkane values from our paleosol samples indicate that the isotopic change began as early as 9 ma reflecting either a growing contribution of c4 plants to a dominantly c3 biomass or a decrease in water availability to c3 plants molecular and isotopic analyses of other compounds including n alcohols and low molecular weightn alkanes indicate paleosol organic matter contains contributions from a mixture of sources including vascular plants algae and or cyanobacteria and microorganisms a range of inputs is likewise reflected in the isotopic composition of the total organic carbon from these samples in addition then alkanes from two samples show little evidence for pedegenic inputs and we suggest the compounds were derived instead from the paleosol s parent materials we suggest the record of vegetation in ancient terrestrial ecosystems is better reconstructed using isotopic signatures of molecular markers rather than bulk organic carbon this approach provides a means of expanding the spatial and temporal records of c4 plant biomass which will help to resolve possible tectonic climatic or biological controls on the rise of this important component of the terrestrial biosphere

holocene sea level change and coastal landscape evolution in the southern gulf of carpentaria australia a revised holocene sea level history for the southern gulf of carpentaria is presented based on new data from the south wellesley archipelago and age recalibration of previous research results confirm that rising sea levels during the most recent post glacial marine transgression breached the arafura sill ca 11 700 cal yr bp sea levels continued to rise to ca 30 m by 10 000 cal yr bp leading to full marine conditions by 7700 cal yr bp sea level reached present mean sea level pmsl and continued to rise to an elevation of between 1 5 m and 2 m above pmsl sea level remained ca 1 5 between 7000 and 4000 cal yr bp followed by rapid regression to within 0 5 m of pmsl by ca 3500 cal yr bp when placed into a wider regional context results from this study show that coastal landscape evolution in the tropical north of australia was not only dependent on sea level change but also show a direct correlation with holocene climate variability specifically the formation and preservation of beach rock deposits intertidal successions beach and chenier ridge systems hold valuable sea level and holocene climate proxies that can contribute to the growing research into lower latitude holocene sea level and climate histories

origin of beach ridges comment on tanner w f 1995 origin of beach ridges and swales mar geol 129 149 161 abstract tanner 1995 has proposed that most common strand plain sandy beach ridges his swash built type have been formed by a sea level rise and fall couplet of 5 30 cm with a periodicity which is most commonly 30 60 years but which ranges from as little as 3 to as much as 60 years while such a mechanism could perhaps apply to beach ridges in lakes if sea level has fluctuated with such regularity for the past several thousand years all open ocean beach ridge periodicities should be the same and furthermore this sea level signal would surely have been detected by physical oceanographers curray et al 1969 described a strand plain of several hundred beach ridges on the western mexican coast with cyclic formation of ridges varying from 12 2 to 16 5 years the mechanism of formation invoked was periodic building of offshore bars to above sea level after sufficient sand had been transported into the area and during an optimal combination of oceanographic conditions

chemical signatures of palaeotsunamis a forgotten proxy article i nfo article history a range of diagnostic criteria are required to help identify palaeotsunami deposits although chemical signatures have long been used as indicators of palaeosalinity in sedimentary sequences their use in the studies of palaeotsunami deposits is rarely applied and is yet to be widely recognised the chemical composition of interstitial water in coastal ponds and sedimentary sequences in coastal marshes and lagoons has been used successfullyasanindicatoroftsunamiinundation chemicalsignaturescanalsoprovidecluesaboutthelandward limit of runup of a tsunami beyond the area of sediment deposition like most palaeotsunami proxies however the preservation of chemical signatures varies with environmental conditions

middle miocene denudation of the higher himalayan crystallines revealed by chemical composition of detrital garnets from the siwalik foreland basin sediments western and central nepal abstract the middle miocene to early pleistocene siwalik group is composed of sediments deposited in the himalayan foreland basin in this study the heavy mineral assemblage and chemical composition of detrital garnets from the sandstones in the lower siwalik sub group which are exposed along the karnali river in western nepal and the tinau khola in central nepal are studied and the provenance shift during the middle miocene is discussed the heavy mineral assemblage in the lower section of the lower siwalik sub group is characterized as predominantly zircon tourmaline rutile chemical analysis of the detrital garnets showed a monomodal almandine rich composition with low pyrope prp

wrack line signatures of high magnitude water level events on the northwest australian coast abstract the pilbara coast is affected by both intense tropical cyclones directing storm surges and high waves from the n and nw and tsunamis generated off indonesia wrack lines of shell and other skeletal material commonly occur not only 2 5 m above australian height datum ahd but also up to 10 m ahd they occur in distinct bands and may be continuous for several kilometres but are usually disjunct for tens of kilometres this study assesses the potential use of wrack lines to identify extreme high water levels preserved on the coast elevated wrack lines occur on open coast dunes storm bars cheniers and spits and along lagoonal shores twelve wrack line assemblages were identified for the last 2500 years with eight reported at more than one site and 5 m ahd six sites contain wrack lines 8 m ahd and three reach 10 m ahd higher than any historical tsunami inundation in the region ten wrack lines are found at 5 8 m ahd and extend beyond the upper end of any reported storm and cyclone wave heights prehistoric wrack lines were also identified at 2 5 m ahd and are within the range of marine inundation by surges associated with present day tropical cyclones

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

origin of beach ridges and swales abstract sandy beach ridges occur in four main categories 1 swash built 2 settling lag 3 eolian 4 storm surge ridges in the first two classes are geometrically regular only a few tens of centimeters above adjacent swales and commonly in ridge sets and systems tens to hundreds of ridges each individual sets of 5 25 ridges tend to stand 0 5 m to 2 m above or below adjacent sets ridges in the third and fourth classes do not have these characteristics do not occur in sets and are generally not suitable for detailed historical studies no one of these ridges is the same as the storm built berm which is almost never preserved swash built sandy beach ridges have diagnostic 1 map spacing 2 accretion rate 3 periodicity 4 crossbedding and 5 granulometry the last two indicate fair weather waves on a sandy beach in contrast with settlinglag ridges postma style which have the same external geometry but which were deposited without important wave work and in contrast with storm built berms generally seen on eroding coasts but rarely or never in beach ridge plains the grain size kurtosis of beach sand is an excellent index to near shore wave energy density changes in kurtosis at ridge set boundaries mark changes in long term wave energy density hence in sea level the latter can be deduced also from set height differences and from spacing differences periodicity is typically 30 60 years map spacing 25 50 m and accretion rate fairly close to 1 m yr a few ridge sets with intervals of 3 7 10 12 or 18 19 years have smaller spacings this is not what can be done if each ridge is built by one storm if each ridge had been built by one storm wide beach ridge plains like one in denmark dating from about 11 700 yr b p would have been formed in the last 30 50 years at accretion rates of hundreds of meters per year instead each swash type sandy beach ridge was made by a sea level rise and fall couplet amplitude 5 30 cm the swale marks the lower position this mechanism reflects the fact that the transverse profile from beach to sea is gently concave upward with maximum curvature close to shore this is a shape which is out of adjustment with the shoaling wave system shortly after a small sea level change settling lag ridges were built without waves hence the ridge and swale sequence in this case cannot be attributed to waves either fair weather or storm these ridges show the same historical pattern as do swash built ridges this fact suggests that both were controlled by the same mechanism sea level change

anatomy of sand beach ridges evidence from severe tropical cyclone yasi and its predecessors northeast queensland australia 1 four well identified tropical cyclones over the past century have been responsible for depositing distinct units of predominantly quartzose sand and gravel to form the most seaward beach ridge at several locations along the wet tropical coast of northeast queensland australia these units deposited by tropical cyclones display a key sedimentary signature characterized by a sharp basal erosional contact a coarser grain size than the underlying facies and a coarse skewed trend toward the base coarse skewed distributions with minimal change in mean grain size also characterize the upper levels of the high energy deposited units at locations within the zone of maximum onshore winds during the tropical cyclone these same coarse skew distributions are not apparent in sediments deposited at locations where predominantly offshore winds occurred during the cyclone which in the case of northeast australia is north of the eye crossing location these sedimentary signatures along with the geochemical indicators and the degraded nature of the microfossil assemblages have proven to be useful proxies to identify storm deposited units within the study site and can also provide useful proxies in older beach ridges where advanced pedogenesis has obscured visual stratigraphic markers as a consequence more detailed long term histories of storms and tropical cyclones can now be developed

mass accumulation rates in asia during the cenozoic summary this work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in asia since the beginning of the cenozoic 66 ma the estimates were derived from isopach maps cross sections and drill holes or stratigraphic columns assuming regional similarity of the strata average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods palaeocene 66 58 ma eocene 58 37 ma oligocene 37 30 and 30 24 ma miocene 24 17 17 11 and 11 5 ma pliocene 5 2 ma and quaternary 2 0 ma these rates shed new light on the geological history of asia since the onset of the collision of india with asia 50 ma the overall average accumulation rates curve for asian sedimentary basins since the beginning of the tertiary shows an exponential form with slow accumulation rates less than 0 5 106 km3 myr 1 until the beginning of the oligocene more than 15 myr after the onset of the collision from the oligocene onwards rates increase quickly in an exponential manner reaching their maximum values in the quaternary more than 1 5 106 km3 myr 1 from these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the india eurasia collision history at smaller scales one may distinguish between independent histories at the subcontinental and basin scales this permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of asia during the cenozoic

dynamic fluvial systems and gravel progradation in the himalayan foreland although the large scale stratigraphy of many terrestrial foreland basins is punctuated by major episodes of gravel progradation the relationships of such facies to hinterland tectonism and climate change are often unclear structural reentrants provide windows into older and more proximal parts of the foreland than are usually exposed and thus provide key insights to earlier phases of foreland evolution our magnetostratigraphic studies show that although the major lithofacies preserved within the himachal pradesh structural reentrant in northwestern india resemble neogene facies in pakistan they have a much greater temporal and spatial variability from 11 5 to 7 ma major facies boundaries in himachal pradesh vary by as much as 2 3 m y across distances of 20 30 km and are controlled by the interference between a major southeastward flowing axial river and a major southwestward flowing transverse river a thick but highly confined middle to late miocene conglomerate facies includes the oldest extensive siwalik conglomerates yet dated 10 ma and implies the development of significant erosional topography along the main boundary thrust prior to 11 ma our studies document extensive syntectonic gravel progradation with conglomerates extending tens of kilometers into the undeformed foreland during a period of increased subsidence rate and within 1 2 m y of major thrust initiation overall gravel progradation is modulated by the interplay among subsidence sediment supply and the proportion of gravels in rivers entering the foreland

siwalik mammals of the jammu sub himalaya india an appraisal of their diversity and habitats abstract the red bed sequence of the lower siwaliks around ramnagar and the nagrota formation of the upper siwaliks in the uttarbeni parmandal section are the two highly fossiliferous intervals of the siwaliks of jammu sub himalaya india the lower siwalik mammalian fauna of ramnagar is best represented in its upper 350 m interval small and medium sized forms mostly belonging to browsing species dominate the mammalian assemblage the ramnagar fauna represents the chinji mammalian fauna middle miocene of the potwar plateau pakistan the assemblage indicates a woodland type ecosystem having substantial forest component and subordinately developed grassy subareas the mammalian fauna of the nagrota formation in the uttarbeni parmandal section in contrast exhibits relatively low species diversity but considerable increase in the mean body size and progressive hypsodonty of the cheek teeth in the herbivores this becomes more pronounced above the 2 5 ma old volcanic tuff layers occurring at the middle of the formation broadly a savanna type ecosystem is indicated by the mammalian communities of nagrota formation which appears to have been dominated by grassland communities above the tuff zone the above tuff faunal zone of the nagrota formation can be correlated with the pinjor faunal zone plio pleistocene of the siwalik hills punjab

austral summer n2o sink and source characteristics and their impact factors in prydz bay antarctica the ocean particularly the southern ocean is considered a significant source of atmospheric n2o which is an ozone depleting greenhouse gas however there are limited data available supporting this conclusion thus this study sampled and analyzed the oceanic n2o in prydz bay the results demonstrated that the distribution of n2o in this embayment differed between the north and south sides of the antarctic slope front asf corresponding to the different hydrographic characteristics on each side although the air to sea n2o flux north of the shelf break is 1 20 0 44 mol m 2 d 1 the source sink characteristics need to be further constrained because the circumpolar deep water cdw may occasionally outcrop over the surface layer the water masses over the continental shelf south of the shelf break may be a temporary or even a permanent n2o sink when sea ice is absent the air to sea flux south of the shelf break is 3 65 0 95 mol m 2 d 1 and the water column is undersaturated with n2o which may result from the deep convection of n2o undersaturated surface water during the winter evidence also suggests that the formation of antarctic bottom water aabw may provide a pathway for n2o removal from the upper layer at high latitudes

isochronous fluvial systems in miocene deposits of northern pakistan a palacomagnetic isochron dated at about 8 1 myr bp and detailed lithostratigraph of a 40 m interval exposed along strike for 40 km establish the depositional patterns of two contemporaneous interfingering fluvial systems in the upper part of the meddle siwalik sequence the two systems referred to as the buff and blue grey differ in unit shape lithofacies bedding sequence palaeocurrent direction and sand composition interfingering occurs along the south west north east strike of the outcrops with the palaeodrainage directions of the two systems generally perpendicular to this line the axis of the blue grey system which deposited widespread sheet sands and silts lay toward the south west end of the study area the more complex axis of the buff system which deposited shoe string sand bodies and lage volumes of silt and clay lay toward the north east the source area for both systems was the rising himalyan belt to the north and noth east of the study area at maximum extent the blue grey system occupied a channel belt at least 25 km wide channel belt widths and depths for the buff system are 1 3 km and 3 7 m respectively current directions averge 94 for blue grey sands and 136 for buff sands blur grey sands contain 20 more rock fragments and are otherwise less mature than buff sands the buff system shows a verticla pattern of avulsion palaeosol formation and floodplain aggradation which we attribute to autocyclic processes of parallel rivers the blue grey system shows phases of erosion accompaniced laterally by plaeosol formation folowed by valley fill and overfowing of interfluve surfaces theis pattern may be caused by allocyclic presses affecting the source area we interpret the blue grey system as a major drainage from the interior himalayas perhaps the ancestral indus and the buff system as a complex of smaller drinages along the mountain front which were probably ributaries to the bluegrey syste vertebrate fossils including hominoid primates from the area are almost exclusively associated with lithofacies of the buff system and this probably refects both taphonomic and palaeoecological differences between the two systems

depositional chronology and fabric of siwalik group sediments in central nepal from magnetostratigraphy and magnetic anisotropy abstract magnetostratigraphic research undertaken within the past 15 years in the siwaliks distributed along 400 km of the sub himalaya in central nepal has proved that the sediments possess highly reliable hematite based primary detrital remanent magnetization suitable to determine depositional chronology in order to bring out the polarity sequences in a common chronological frame all available data are newly correlated to the latest global magnetic polarity time scale of cande and kent s c cande d v kent 1995 revised calibration of the geomagnetic polarity timescale for the late cretaceous and cenozoic journal of geophysical research 100 6093 6095 chronological data presented are referred in relation to the diverse lithological nomenclature to the formations whose ages are not constrained by isotopic or paleontologic ages the age of the sections dated by magnetostratigraphy ranges between 14 and

confirmation of a late miocene subchron c4n 2n 1r from the eastern qaidam basin in the ne tibetan plateau

inclination flattening and the geocentric axial dipole hypothesis abstract william gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis the gad hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude for decades there have been calls for permanent non dipole contributions to the time averaged field recently these have demanded large contributions of the axial octupole which if valid would call into question the general utility of the gad hypothesis in the process of geological recording of the geomagnetic field earth filters distort the directions many processes for example sedimentary inclination flattening and random tilting can lead to a net shallowing of the observed direction therefore inclinations that are shallower than expected from gad can be explained by recording biases northward transport or non dipole geomagnetic fields using paleomagnetic data from the last 5 million years from well constrained lava flow data allows the construction of a statistical geomagnetic field model such a model can predict not only the average expected direction for a given latitude but also the shape of the distribution of directions produced by secular variation the elongation of predicted directions varies as a function of latitude from significantly elongate in the up down direction at the equator to circularly symmetric at the poles sedimentary inclination flattening also works in a predictable manner producing elongations that are stretched side to side and the degree of flattening depending on the inclination of the applied field and a flattening factor f the twin tools of the predicted elongation inclination relationship characteristic of the geomagnetic field for the past 5 million years and the distortion of the directions predicted from sedimentary inclination flattening allows us to find the flattening factor that yields corrected directions with an elongation and average inclination consistent with the statistical field model the method can be tested using sediments deposited in a known field application of the elongation inclination correction method to two magnetostratigraphic data sets from red beds in asia and pakistan brings the inclinations into agreement with those predicted from modern gps measurements and from global paleomagnetic data there appears to be no compelling reason at this time to abandon the geocentric dipole hypothesis which has provided such an excellent working model for so long

magnetic polarity stratigraphy of siwalik group sediments of karnali river section in western nepal the remanent magnetization of siltstones and sandstones sampled at 476 levels sites throughout a 3560 m thick molasse sequence belonging to the siwalik group 0 2015 m lower 2015 3560 m middle has been studied by stepwise thermal demagnetization this section is exposed along the karnali river in nepal the natural remanent magnetization nrm usually consists of two components a viscous or thermoviscous component of recent field origin and an ancient characteristic component chrm the former component is of normal polarity and resides either in goethite unblocking temperature 150 c resistant to afd up to 150 mt or in maghemite unblocking temperature 150 400 c goethite contributes up to 90 per cent of the total intensity in the finer variegated muddy samples belonging to the lower half of the section maghemite content is significant in the grey mud free lithologies from the upper half of the section the main component unblocked in the high temperature range commonly 610 680 c and believed to reside in haematite presumably of mostly detrital origin represents a characteristic remanence chrm the tilt corrected chrm directions at individual sites show antipodal clusters ratio of normal to reverse polarity sites 0 62 and yield mean inclinations recording significant inclination shallowing a feature well recorded in the siwaliks this chrm is interpreted to represent a largely primary detrital remanence the chrm data from 430 sites yield the karnali river magnetic polarity sequence whose correlation with the geomagnetic polarity timescale cande kent 1995 suggests a depositional age of 16 ma younger than chron c5cn 1n to 5 2 ma around the top of chron c3r for the 3560 m section sampled hence the karnali river exposes the oldest part of the siwalik group in nepal estimates of the sediment accumulation rate sar average to 32 9 cm kyr 1 for the 10 8 myr time span of deposition

lagoon subsidence and tsunami on the west coast of new zealand abstract sediment core and trench data from a coastal lagoon on the west coast of the south island new zealand are used to investigate evidence for co seismic subsidence and associated tsunami inundation physical data are used to document a salt marsh soil buried 80 cm below the modern sediment surface that is locally covered by a gravelly sand bed the sediment record also contains geochemical and biological diatom and foram evidence for abrupt changes in salinity of lagoon waters that link to subsidence tsunami flooding and to the open versus closed state of the lagoon tidal entrance at the local scale these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon we also propose a conceptual connection between these local changes and regional drivers of landscape development most notably major earthquakes and resultant pulses in sediment supply to the coast

fluvial and lacustrine palaeoenvironments of the miocene siwalik group khaur area northern pakistan the miocene siwalik group upsection the chinji nagri and dhok pathan formations in northern pakistan records fluvial and lacustrine environments within the himalayan foreland basin thick 5 m to tens of metres sandstones are composed of channel bar and fill deposits of low sinuousity 1 08 1 19 single channel meandering and braided rivers which formed large low gradient sediment fans or megafans river flow was dominantly toward the south east and likely perennial palaeohydraulic reconstructions indicate that chinji and dhok pathan rivers were small relative to nagri rivers bankfull channel depths of chinji and dhok pathan rivers were generally 15 m and up to 33 m for nagri rivers widths of channel segments including single channels of meandering rivers and individual channels around braid bars were 320 710 m for chinji rivers 320 1050 m for nagri rivers and 270 340 m for dhok pathan rivers mean channel bed slopes were on the order of 0 000056 0 00011 bankfull discharges of channel segments for chinji and dhok pathan rivers were generally 700 800 m3s 1 with full river discharges possibly up to 2400 m3s 1 bankfull discharges of channel segments for nagri rivers were generally 1800 3500 m3s 1 with discharges of some larger channel segments possibly on the order of 9000 32 000 m3s 1 full river discharges of some of the largest nagri braided rivers may have been twice these values thin decimetres to a few metres sandstones represent deposits of levees crevasse channels and splays floodplain channels and large sheet floods laminated mudstones represent floodplain and lacustrine deposits lakes were both perennial and short lived and likely less than 10 m deep with maximum fetches on the order of a few tens of kilometres trace fossils and body fossils within all facies indicate the former existence of terrestrial vertebrates molluscs bivalves and gastropods arthropods including insects worms aquatic fauna e g fish turtles crocodiles trees bushes grasses and aquatic flora palaeoenvironmental reconstructions are consistent with previous palaeoclimatic interpretations of monsoonal conditions

geomagnetic reversals and excursions their paleomagnetic record and implications for the geodynamo since the earliest reports of paleomagnetic evidence in support of the existence of geomagnetic field reversals much attention has been focused on understanding the relevant core mechanism given the far reaching implications such an understanding would have on the whole of geomagnetism past investigations of this phenomenon have involved experimentalists and theoreticians alike in particular during the previous quadrennium 1975 1978 significant contributions were gained from each of various approaches namely experimental studies of paleomagnetic records of polarity transitions statistical studies involving the frequency of occurrence of reversals as well as the time averaged full polarity states and theoretical studies concerning the dynamo continued progress along many fronts has been made during the last four years see the recent review by hoffman 1982a such is the subject of this report

the magnetic polarity stratigraphy of the siwalik group at haritalyangar india and a new last appearance datum for ramapithecus and sivapithecus in asia abstract the haritalyangar india local fauna contains type specimens of several hominoid primates which are assigned a new last appearance datum age based on a magnetic polarity stratigraphy this youngest assigned age for sivapithecus indicus s sivalensis and ramapithecus punjabicus in asia is about 7 0 7 5 m y the age of the holotype specimen of gigantopithecus bilaspurensis is about 6 3 m y the nahan sandstone formation is at least in part contemporary with the nagri formation lithofacies of the potwar plateau pakistan

coalescence megafan multistorey sandstone complex of the late orogenic mio pliocene sub himalayan belt dehra dun india in the himalayan foreland basin a prominent multistorey sandstone complex in the middle siwalik subgroup is exposed along the southern flank of the dehra dun valley in the mohand anticline extending laterally for 40 km the middle siwalik subgroup consists of sandstone mudstone couplets 300 450 m thick in the lower part and the multistorey sandstone complex 900 1200 m thick in the upper which forms a gross coarsening upward sequence the major lithofacies are trough cross stratified sandstone planar cross stratified sandstone ripple drift laminated sandstone horizontal laminated sandstone and massive sandstone with subordinate amounts 20 of mudstone and conglomerate the multistorey sandstone complex is punctuated by several erosional surfaces over which abundant mud clasts are present the trough cross stratification exhibits a dominantly southward palaeoflow with much variation in the southeast and southwest quadrants however at outcrop level the palaeoflow data reveal internal consistency this spatial and temporal variability in palaeoflow direction indicates the existence of two major drainage systems of coalescing alluvial megafan type the estimated palaeochannel sinuosity is of the order of 1 04 to 1 23 with a return period of 4 to 8 103 years palaeoflow variability facies distribution frequent avulsion and the coarsening upward sequence collectively suggest the progradation of coalescing alluvial fans towards the south and southwest this was principally controlled by thrust movements and differential basin subsidence at the margin of the himalayan orogen

distributions of n2o and its air sea fluxes in seawater along cruise tracks between 30 s 67 s and in prydz bay antarctica 1 air and surface seawater samples were taken during the 22nd chinese national antarctic research expedition november 2005 to march 2006 and analyzed for n 2 o concentrations the results show that the concentration of n 2 o in surface seawater increased from 8 9 0 2 nm to 17 9 0 3 nm along the cruise tracks southward from 30 s 67 s latitude and correlated well with sea surface temperature sst the saturation anomaly along the cruise tracks changed from negative south to positive north with the turning point located between 50 and 55 s latitude coincident with the location of the subantarctic front saf positive saturation found north of the saf is due to the seasonal sst variation while the undersaturation of n 2 o south of the saf may be due to a combination of sst variation and intrusion of n 2 o depleted ice meltwater during summer air sea fluxes measured on the cruise tracks north of the saf were positive ranging between 5 and 10 mol m 2 d 1 while fluxes south of the saf were close to zero n 2 o in the surface water of prydz bay was in near equilibrium with the atmosphere the corresponding air sea flux was about 0 3 0 8 mol m 2 d 1 not different from zero

the origin of centennial to millennial scale chronological gaps in storm emplaced beach ridge plains recent studies of tropical cyclone surge and wave emplaced beach ridge plains have shown that these sequences often contain centennial to millennial scale gaps in their chronologies two explanations for the gaps exist they are due to erosion or alternatively a cessation or substantial slowing of depositional processes suggestive of a quieter phase in intense storm activity differentiating between the two is important for uncovering reliable long term storm histories from these sequences we use landform morphology sediment texture and luminescence chronology to determine the origin of substantial chronological gaps in a plain containing more than 100 shore parallel ridges composed of fine grained sand located in northeast australia we identify and describe the characteristics associated with both erosional and non erosional gaps the erosional gaps are associated with changes in orientation between ridge sets and often a high ridge with hummocky topography that appears to have been disturbed by aeolian activity river floods likely caused the partial erosion of ridge sets non erosional gaps do not display these morphological characteristics and are likely associated with quiescence in severe tropical cyclone activity these geomorphic and chronological signatures can be used to identify different sorts of gaps in other ridge plains and are an important tool in the reconstruction of long term storm histories from these coastal landforms the data also suggests that fine grained ridges can like their coarse grained counterparts be predominantly deposited by storm waves and surge and their texture need not necessarily be indicative of the processes responsible for ridge development

siwalik age faunas from the himalayan foreland basin of south asia abstract the himalayan foreland basin is characterised by three principal sedimentary successions these are the subathu group palaeocene eocene the murree or dharamsala group oligocene miocene and the siwalik group miocene pleistocene the basin was linked in the east to the bay of bengal through the bengal basin and its western part was connected to the arabian sea through rajasthan and kachchh gujarat the himalayan foothills have long been known for yielding rich mammalian fossil occurrences and significant localities in the indian siwaliks include kalagarh ramnagar haritalyangar chandigarh and jammu regions the bugti basin and zinda pir area of sulaiman range of pakistan were also part of the foreland basin as lower and middle siwalik fossils are known from the vihowa and litra formations respectively the marwat formation of bhittani and marwat ranges pakistan have also yielded pinjor age vertebrate fossils the middle and upper siwalik age fossils are also known from the irrawaddy formation of myanmar where older pegu beds have also yielded scanty lower siwalik age fossils this faunal succession in the irrawaddy valley may have geologically and biogeographically belonged to the himalayan foreland basin in the past additional mammalian fossils having an affinity with the lower and middle siwaliks are known from the khari nadi formation of kachchh the bokabil formation of tripura also yielded scanty lower to middle siwalik fossils a younger siwalik late miocene assemblage is known from piram island of gujarat these areas are also part of the foreland basin most recently a late miocene suid species was discovered and reported from near baripada odisha the paper discusses the respective faunal lists of the various successions mentioned above finally the paper discusses the implications of the foreland faunas the faunas of lower and middle siwaliks of foreland basin have links with europe turkey africa and central asia and throw light on the uplift of the himalaya the post siwalik faunas of central and peninsular india and indo gangetic plains have also yielded remnant siwalik taxa including stegodon insignis elephas hysudricus and potamochoerus theobaldi the kurnool cave fauna and recent fauna of india have also generic resemblance with the foreland faunas

fidelity and time resolution of the magnetostratigraphic record in siwalik sediments high resolution study of a complete polarity transition and evidence for cryptochrons in a miocene fluviatile section summary the surai khola section in southwest nepal a 5000 m continuously exposed record of fluvial sedimentation since middle miocene was revisited for high resolution magnetostratigraphy in sequences with expected cryptochrons and reversals of the geomagnetic field polarity intervals with durations of a few tens of thousands of years are recorded as zones of stable palaeomagnetic directions polarity transitions are recorded as zones with complex demagnetization behaviour of specimens in the sedimentary column almost antiparallel palaeoremanence directions residing in diverent haematite phases in the same specimens could generally not be separated properly by thermal demagnetization divering demagnetization paths for neighbouring specimens during a reversal suggest that measured transitional directions are not true geomagnetic field directions but rather are generated by the superposition of variable amounts of at least two almost antiparallel components of magnetization accompanying studies of recent river sand deposits demonstrate that these sediments acquire a true depositional remanent magnetization drm with considerable inclination errors and scattered directions for individual specimens

negatively skewed aeolian sands from a humid tropical coastal dunefield northern australia abstract this paper describes the nature and environmental significance of variations in textural parameters within a large coastal dunefield in tropical northern australia grain size parameters of modern beaches and foredunes are very similar but are distinct from those of parabolic dune and sandplain environments on average beach and foredune sands have a normal grain size distribution but parabolic dune sands are predominantly negatively skewed negative skewness is interpreted as primarily reflecting sorting of dune sediments by winnowing at dune crests and by avalanching on slip faces a general relationship between mean size and skewness is supported with finer sediments showing increased negative skewness positive skewness can therefore not be used as a diagnostic property of aeolian sediments

geochemical signatures up to the maximum inundation of the 2011 tohoku oki tsunami implications for the 869 ad jogan and other palaeotsunamis abstract the geochemical signature of the tohoku oki tsunami deposit and underlying soil was assessed two months five months and seven months after the 11 march 2011 tsunami inundated the sendai plain the extent of the recognisable sand deposit was traced up to 2 9 km inland while a mud deposit was found up to 4 65 km inland representing 60 and nearly 95 of the maximum tsunami inundation respectively the limit of tsunami inundation was identified 4 85 km from the shore using geochemical marine markers s and cl two months after the tsunami in the absence of any sedimentological evidence concentrations of other geochemical markers k ca sr indicative of the marine incursion and associated minerals were found to decrease landward 13 c and 15 n and c n ratios suggested a mixture of terrestrial and marine organic sources in the sediment while 34 s of sulphate reflected the marine source of water soluble salts the chemical composition of the 869 ad jogan tsunami sand deposit was characterised by high sr and rb concentrations and was comparable to that of the tohoku oki tsunami deposit suggesting that the sources of sediment may be similar marked decreases in s and cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments however both s and cl markers as well as sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami this suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition in particular when marine microfossils are sparse or lacking as is the case on the sendai plain this would allow researchers to redraw palaeotsunami inundation maps and re assess the magnitude of events such as the jogan tsunami and other palaeotsunamis not only on the sendai plain but also elsewhere around the world this has important implications for tsunami risk assessment hazard mitigation and preparedness

paleomagnetism of the middle siwalik formations of northern pakistan and rotation of the salt range decollement abstract sampling for paleomagnetic study has been carried out at seven localities in the potwar plateau region of pakistan in the vicinity of the salt range in all 253 sites consisting of three samples per site were studied the sites were taken from the chinji nagri dhok pathan and upper siwalik formations which span the last 14 m y of earth history the formations have been deformed in the ongoing himalayan orogeny and are exposed today in sections which dip at angles of from 10 to 90 in different directions a characteristic direction of magnetization was isolated at all sections by thermal demagnetization at temperatures of from 550 to 650 c the sediments have been folded within the last 2 m y and because of a positive fold test it can be shown that the characteristic magnetization of these sediments was acquired before folding four of the sections have directions of magnetization which have been rotated in a counter clockwise fashion up to 40 however sections taken along the indus river the north flank of the soan syncline and the south flank of the salt range show small counter clockwise rotations of under 10 these observations are in agreement with previous suggestions that strata in the salt range have been moved to the south and rotated in a counter clockwise fashion the observations reported here indicate that the paleomagnetic poles derived from cambrian and permian formations within the salt range have probably also suffered rotation and should be removed from consideration in gondwanaland reconstruction of the paleozoic

nitrous oxide in the bellingshausen sea and drake passage concentrations of dissolved and atmospheric nitrous oxide n2o were measured in the austral spring of 1992 in the drake passage and bellingshausen sea as part of the united kingdom joint global ocean flux study expedition to the southern ocean the measured atmospheric mixing ratio was 313 5 parts per billion by volume in agreement with the hemispherically corrected global mean in the drake passage surface n2o saturations were generally very close to atmospheric equilibrium 99 7 3 although several anomalous points were associated with the presence of frontal and eddy like features within the antarctic polar frontal zone and at the continental water boundary further to the south a series of oceanographic stations and two surface transects along the 85 w meridian between 65 28 s and 70 32 s revealed a transition from undersaturated conditions in open water to oversaturated conditions in the marginal ice zone in the upper mixed layer 75 100 m these observations reflect upwelling of circumpolar deep water at approximately 70 s resulting in the accumulation of n2o under the winter sea ice and its subsequent release to the atmosphere following the ice retreat sea air n2o fluxes were estimated from the product of the surface n2o anomaly and the modeled gas transfer coefficients of liss and merlivat 1986 and wanninkhof 1992 to find a maximum rate of 3 1 mol n2o m 2 d 1 north of the upwelling region antarctic surface water formed from the mixing of surface waters and ice melt was moderately depleted in n2o with respect to the atmosphere a minimum 90 of saturation this sink area was estimated to extend between 65 28 s and 69 57 s with a mean sea air flux of between 0 6 0 4 and 0 9 0 7 mol n2o m 2 d 1 the region studied at 85 w 65 28 s to 70 32 s revealed source and sink areas which were largely determined by the changing physical hydrography so that overall there was a small net negative flux of between 0 06 0 9 and 0 09 1 4 mol n2o m 2 d 1

isotopic versus micrometeorologic ocean co2 fluxes a serious conflict eddy correlation measurements over the ocean give co2 fluxes an order of magnitude or more larger than expected from mass balance measurements using radiocarbon and radon 222 in particular smith and jones 1985 reported large upward and downward fluxes in a surf zone at supersaturations of 15 and attributed them to the equilibration of bubbles at elevated pressures they argue that even on the open ocean such bubble injection may create steady state co2 supersaturations and that inferences of fluxes based on air sea pco2 differences and radon exchange velocities must be made with caution we defend the global average co2 exchange rate determined by three independent radioisotopic means prebomb radiocarbon inventories global surveys of mixed layer radon deficits and oceanic uptake of bomb produced radiocarbon we argue that laboratory and lake data do not lead one to expect fluxes as large as reported from the eddy correlation technique that the radon method of determining exchange velocities is indeed useful for estimating co2 fluxes that supersaturations of co2 due to bubble injection on the open ocean are negligible that the hypothesis that smith and jones advance cannot account for the fluxes that they report and that the pco2 values reported by smith and jones are likely to be systematically much too high the co2 fluxes for the ocean measured to date by the micrometeorological method can be reconciled with neither the observed concentrations of radioisotopes of radon and carbon in the oceans nor the tracer experiments carried out in lakes and in wind wave tunnels

holocene evolution of the chan may coastal embayment central vietnam changing coastal dynamics associated with decreasing rates of progradation possibly forced by mid to late holocene sea level changes abstract southeast asian coastal environments are undergoing massive transformations with unprecedented population and infrastructure development these transformations are occurring on a backdrop of intense natural and anthropogenic environmental change which are increasing the risk to the burgeoning coastal population little is known about how central vietnamese coastal environments have changed naturally since the mid holocene sea level highstand and how recent anthropogenic change and sea level variation have affected the coastal system the chan may embayment in central vietnam allows us to examine how recent changes in both anthropogenic development and sea level change have affected the coastline the embayment preserves a series of prograding beach ridges and is subject to intense human pressures with the construction of a large economic and industrial park and expansion of tourist facilities using ground penetrating radar and quartz optical dating we identify a switch from 6000 years of prograding beach ridges to transgressive dunes within the past century resulting in a decreasing rate of beach ridge progradation possibly in the last 100 years the recent modes of sediment deposition through washovers and a transgressive dune indicates that coastal progradation has slowed and might have stopped

origin of beach ridges reply abstract the important difference here is whether or not sea level can change by the right amounts and on the right schedule curray says no however various reports in the recent literature cited below show that he is mistaken likewise his concept of uniform global change is not supported by the published data sea level does change at relatively short intervals years decades by amounts that are adequate to produce individual sandy beach ridges and this change is not uniform at all places my citation of curray and others for an 18 6 year period in one sandy beach ridge plain was an inadvertent error and i apologize for it my caveat that we do not know that his study area in a well known modern deformational belt was completely stable throughout the holocene is still valid the corollary data obtained from such areas may not be as useful as information from other areas therefore the presumed 18 6 yr cycle is suspect ab initio curray s hypothesis that beach ridges are initiated by what is basically the suggestion of de beaumont does not provide a suitable model as is discussed below finally curray disregards the detailed granulometric analysis which was the basis for most of my work this modern analysis can stand alone if necessary and is not affected in any significant way by warping or other small deformation however the present availability of records of small modern sea level changes confirms the reasonableness of the timing and magnitudes which were deduced as part of the granulometric work

late cenozoic fluvial successions in northern and western india an overview and synthesis abstract late cenozoic fluvial successions are widespread in india they include the deposits of the siwalik basin which represent the accumulations of the ancient river systems of the himalayan foreland basin palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by himalayan tectonics as well as by major climatic fluctuations during the long 13 ma span of formation the indo gangetic plains form the world s most extensive quaternary alluvial plains and display spatially variable controls on sedimentation himalayan tectonics in the frontal parts climate in the middle reaches and eustasy in the lower reaches close to the ganga brahmaputra delta climatic effects were mediated by strong fluctuations in the sw indian monsoon and himalayan rivers occupy deep valleys in the western ganga plains where stream power is high cut in part during early holocene monsoon intensification the broad interfluves record the simultaneous aggradation of plains fed rivers since 100 ka the eastward increase in precipitation across the ganga plains results in rivers with low stream power and a very high sediment flux resulting in an aggradational mode and little incision the river deposits of semi arid to arid western india form important archives of quaternary climate change through their intercalation with the eolian deposits of the thar desert although the synthesis documents strong variability both spatial and temporal in fluvial stratigraphy climatic events such as the decline in precipitation during the last glacial maximum and monsoon intensification in the early holocene have influenced fluvial dynamics throughout the region

integrating sieving and laser data to obtain bulk grain size distributions abstract it is not always possible to use a single technique to determine the complete grain size distribution of a natural sediment namely when dealing with successions of variable grain size or with sediments or soils that contain silt clay and sand gravel populations in this work we assess the feasibility of using laser diffraction to measure sand size particles by analyzing the representativeness of laser samples and quantifying the deviations between results of sieving and laser diffraction four groups of sediments with different grain size distributions and proportion of heavy minerals were compared it is demonstrated that the risk of laser sample underrepresentativeness is higher when measuring grains coarser than 1 mm in particular when clay silt particles are also frequent depending on the size fraction the divergence between the results of sieving and laser diffraction due to shape and density effects is variable and not easy to predict quantitatively given these uncertainties it is proposed to use different computational threshold diameters that separate the fractions considered by sieving and laser diffraction and measure part of the distribution with both techniques we developed a flexible computer application that allows users to visually compare different possibilities of combined laser sieving grain size distribution curves and to choose the best option of threshold diameter the best combined results can then be used to model the grain size distribution

paleomagnetic stratigraphy and time in sediments studies in alluvial siwalik rocks of pakistan sediments may acquire magnetic remanence upon deposition and shortly after deposition hence the paleomagnetic record of sedimentary rocks may provide a chronostratigraphic framework for rates and patterns of depositional and post depositional processes over time scales intermediate between those of modern observation and those of the dated geologic record two applications of high resolution magneto stratigraphy in miocene alluvial rocks of pakistan illustrate this point 1 transition stratigraphy the dense sampling of a magnetic reversal of correlated sections in the dhok pathan formation revealed high variability in sediment accumulation rates over several thousand to 10 000 yr time transgressive strata representing a paleosol and a floodplain marsh and a pervasive post depositional record mainly from pedogenesis 2 lateral tracing of paleomagnetic reversal boundaries in the chinji formation revealed a secular change in sediment accumulation rate and evidence for increased accumulation rate a

gravity anomalies flexure of the indian plate and the structure support and evolution of the himalaya and ganga basin bouguer gravity anomalies along four profiles across the western himalaya and ganga basin show large deviations from local isostatic equilibrium a deficit of mass characterizes the ganga basin and an excess underlies the lesser himalaya both can be understood if the indian plate is flexed down by the distributed load of part of the mountains the cross sectional shape of the ganga basin seems to be controlled by the deflection of the indian plate which we compute assuming the indian plate to overlie an inviscid fluid from the shapes of both bouguer anomaly profiles and the basement topography we place bounds on the flexural rigidity of such a plate if the ganga basin is a steady state feature then the age of the basal sediments in a given locality should be proportional to the distance of that locality from the southern edge of the basin if the rate of convergence of india and the himalaya were constant that rate should equal the distance divided by the corresponding age we find a rate of 10 to 15 mm a for the last 15 to 20 ma which is consistent with a large part of the 50 mm a rate of convergence between india and eurasia being absorbed by the eastward extrusion of parts of tibet profiles of bouguer gravity anomalies show only a small peak or plateau over the southern edge of the lesser himalaya implying that the boundary between the light sediments of the ganga basin and the heavier crustal rocks of the lesser himalaya is not sharp and that there exists some light material beneath the range we infer that some sediment deposited in the ganga basin has been underthrust beneath the lesser himalaya but the quantity is small most of this sediment probably is scraped off the indian plate to make the foothills of the range we find that the load of the high himalaya is too large to be supported solely by elastic stress in the indian plate if the flexural rigidity of the plate is constant and if no other external forces act on the plate the observed gradient in bouguer gravity anomalies increases from an average of about 1 mgal km over the ganga basin and lesser himalaya to about 2 mgal km over the high himalaya this increase in the gravity gradient implies that the moho dips more steeply 10 15 beneath the high himalaya than beneath the lesser himalaya 2 3 we interpret this steepening of the moho to be due to a weakening of the plate which allows it to bend more sharply beneath the high himalaya than farther south with the inclusion of a weak segment of indian plate beneath the high himalaya calculated anomalies show a somewhat increased gradient beneath the high himalaya but when the weight of the entire himalaya is used as a load on the plate calculated anomalies are more negative than observed therefore an external force system is needed to support much of the weight of the high himalaya as well as to bend the plate sufficiently beneath the high himalaya the magnitudes of the bending moment and the force per unit length that must be applied to the end of the plate are compatible with their sources being gravity acting on a part of india s mantle lithosphere stripped of its crust and underthrust beneath southern tibet

new muroid rodent and sivapithecus dental remains from the lower siwalik deposits of ramnagar j k india age implication abstract this paper reports a murid rodent antemus chinjiensis and a cricetid rodent megacricetodon cf sivalensis in addition to sivapithecus from the famous miocene ape locality of ramnagar jammu and kashmir india in the absence of numerical dates mammalian biochronology in general and rodent biochronology in particular provides good temporal resolution for terrestrial fossil sites by using the well established high resolution siwalik rodent biochronology the ramnagar assemblage can now be constrained between at least 13 2 and 13 8 ma this preliminary biochronological framework has the potential of increasing the first appearance datum fad of sivapithecus from the presently estimated 12 8 ma to at least 13 2 ma

a biostratigraphic zonation of the middle and upper siwaliks of the potwar plateau of northern pakistan abstract two biostratigraphic reference sections are designated for the middle and upper siwalik formations of northern pakistan the stratigraphic ranges of 41 mammalian taxa are established in the reference sections and the two sections are correlated to each other and to the standard magnetic polarity time scale by the magnetic polarity stratigraphy the resulting stratigraphic and magnetostratigraphic framework is used to define four contiguous biostratigraphic interval zones the proposed interval zones are bounded by five important faunal events which are identified in the reference sections the four proposed interval zones and the approximate ages in the reference sections of their lower and upper boundaries are 1 the hipparion s l interval zone 7 4 9 5 m y b p 2 the selenoportax lydekkeri interval zone 5 3 7 4 m y b p 3 the hexaprotodon sivalensis interval zone 5 3 2 9 m y b p and 4 the elephas planifrons interval zone 2 9 1 5 m y b p the paleomagnetic and biostratigraphic evidence indicates that the tatrot beds from which pilgrim developed his tatrot faunal zone are between 2 5 and 3 4 m y b p with a preferred maximum age of 2 9 m y b p the biostratigraphic evidence indicates the sethi nagri locality y311 the primary source of pilgrim s nagri faunal zone is in the hipparion s l interval zone the paleomagnetic evidence suggests an approximate age of 9 m y b p a major faunal event at 9 5 m y b p introduced equids suids and large giraffes from eurasia into the indain subcontinent a second more diffuse faunal event between 5 3 and 2 9 m y b p introduced several african taxa as well as equus and cervids from eurasia

relative sea level records preserved in holocene beach ridge strandplains an example from tropical northeastern australia abstract northeastern queensland is a far field site from ice caps formed during the last glacial however the region has experienced glacio hydroisostatically driven coastal elevation change during the holocene that generated a distinctive relative sea level record we tested whether this subtle vertical movement of the coast is recorded in the morphology and stratigraphy of the beach ridge strandplain at cowley beach which comprises a series of 36 prominent and several subdued or truncated beach ridges previous studies have shown that the strandplain records the long term progradation of the coast with the ridges comprising coarse medium sand that was deposited during both fairweather foreshore and berm facies and tropical cyclone events erosional unconformities storm surge deposits over the past approximately 7 ka we utilised a fine scale digital elevation model of the strandplain to examine beach ridge morphology and to compare the elevation pattern with published holocene sea level data for the region the overall elevation pattern of the strandplain surface is consistent with the regional sea level history that includes a highstand at around 6 ka bp generated by isostatic uplift and the elevation of the berm facies matches well robust coral sea level indicator data we also modelled the strandplain topographic patterns that would result under stable and continually rising holocene sea levels the frequencies of elevation classes across the strandplain are normally distributed when the strandplain is deposited during a period of stable sea level and negatively skewed with a continually rising sea level consistent with the expected patterns the results indicate the sensitivity of the elevation of the top of the berm facies preserved in beach ridges to subtle changes in sea level tens of cm over a thousand years our results further underline the utility of beach ridge strandplains a globally distributed coastal landform for building relatively detailed regional records of sea level during the holocene at sites currently lacking this information

a biogeochemical study in the bellingshausen sea overview of the sterna 1992 expedition abstract a general overview and background of a two ship study to examine biogeochemical fluxes in the marginal ice zone of the bellingshausen sea 65 70 s 80 87 w se pacific sector of the southern ocean is presented the major feature studied was an intense band of chlorophyll that was found geographically close to a receding ice edge however the bloom appeared not to be a result of a shallow mixed layer caused by ice melt stabilisation but rather associated with an oceanic front that coincided with the ice edge details of the hydrographic conditions existing along the 85 w meridian from the ice edge to open water to the north and detailed surveys of surface hydrographic conditions are presented

sand beach ridges record 6000 year history of extreme tropical cyclone activity in northeastern australia sand beach ridges are considered to be derived either from aeolian processes and or waves but their deposition by individual or multiple storms has not been investigated in any detail we use numerical meteorological and oceanographic models to determine the origin of a sequence of 29 shore parallel sand beach ridges in northeastern australia the results suggest that the ridges were constructed by waves and that the final form or height of the ridges is a function of high energy tropical cyclone generated waves plus storm tides hence these landforms archive a nearly 6000 year long history of intense tropical cyclones the record implies that these extreme tempests occur considerably more frequently than that suggested by the short historical record for this region the genesis of this sand beach ridge plain has implications for the interpretation of similar sequences elsewhere along the northeast coast of australia and in comparable environments globally if other similar sand beach ridge plains have also been deposited by like processes it stands to reason that these long term records of high intensity tropical cyclones can be used to ascertain a regional scale risk assessment from this hazard

magnetic polarity stratigraphy and ages of siwalik group rocks of the potwar plateau pakistan abstract six magnetic polarity sections have been established over the potwar plateau region of pakistan including the major stratotypes of the siwalik group in all six sections the dominant feature of the magnetic polarity stratigraphy is a long normal polarity zone which is contained within the nagri formation this conspicuous normal polarity zone has been radiometrically dated at 9 5 0 6 m y which identifies it as magnetic chron 9 radiometric dates from the upper siwalik formation have also been used to identify the chron 2 3 boundary in two of the sections the magnetic polarity stratigraphy of three of the sections has been correlated securely with the accepted magnetic polarity time scale so that the ages of the local stratigraphy are indexed accordingly based exclusively on data from stratotype sections the chinji nagri and dhok pathan formations have nominal age ranges of 10 1 13 1 7 9 10 1 and 5 1 7 9 m y age fluctuations on the order of 105 years may be anticipated for these formational boundaries within radius of some 20 km of the designated stratotype mean sediment accumulation rates during the chinji nagri and dhok pathan interval range from 13 to 52 cm 103 yr essentially linear sediment accumulations are locally maintained over time intervals of several million years the chinji nagri lithofacies boundary marks a transition from slow to faster sediment accumulation over much of the potwar plateau indicating a fundamental sedimentary tectonic change at this time

tectonic impact on the fluvial deposits of plio pleistocene himalayan foreland basin india abstract the himalayan foreland basin comprises a number of subbasins developed in various sedimentary environments during the plio pleistocene phases of himalayan orogeny this paper describes the evolutionary processes that led to the development of the himalayan foreland basin in the dehra dun and subathu subbasins the dehra dun subbasin essentially consists of conglomerate facies whereas subathu subbasin is primarily composed of sandstone mudstone intercalated with conglomerate the two subbasins were sites of braided river systems evidence from chronostratigraphy provenance and tectonic and climatic conditions suggests that differential tectonic movement sedimentation rate and basin subsidence coupled with climatic variation were responsible for the contrasting fluvial facies in these subbasins following the merger of the two subbasins at about 5 23 ma the conglomerate facies assemblage of the dehra dun subbasin passes laterally into a sandstone mudstone conglomerate facies assemblage of the subathu subbasin thickly bedded amalgamated sheet conglomerate of dehra dun subbasin has a high sedimentation rate 0 70 mm year between 5 23 and 4 8 ma with a slow rate of basin subsidence in contrast a slow sedimentation rate 0 39 mm year in coeval sediments of the subathu subbasin with relatively fast subsidence produced a succession of thick multistorey sandstone body with mature paleosols petrographic and clast composition data from dehra dun subbasin suggest that the detritus was derived from the pre tertiary lesser himalayan sequence lying in the north during an active tectonic phase of the main boundary thrust between 4 8 and 1 77 ma progradation of posttectonic conglomerate of the dehra dun subbasin continued during a quiescent phase of the main boundary thrust however as a consequence of partitioning of subathu subbasin along the intra foreland thrust interfingering of buff piedmont drainage and grey trunk drainage sandstones took place in contrast the syntectonic conglomerate of subathu subbasin originated from the uplifted proximal part of the foreland basin tertiary belt during the active phase of intra foreland thrust around 1 77 ma

magnetic polarity stratigraphy of the neogene siwalik group at khutia khola far western nepal the middle miocene pliocene siwalik group was deposited in the himalayan foreland basin in response to uplift and erosion in the himalayan fold thrust belt results of thermal demagnetization experiments on samples from the siwalik group in central and western nepal demonstrate that laminated siltstones yield paleomagnetic data useful for tectonic and magnetostratigraphic studies sandstones and paleosols of the siwalik group however generally display highly erratic paleomagnetic behavior during thermal demagnetization on the basis of these observations siltstones from a well exposed 2423 m thick section of the siwalik group in khutia khola far western nepal were sampled for magnetic polarity stratigraphy the siwalik group is composed of informal lower middle and upper members correlation of the resulting polarity stratigraphy with the geomagnetic polarity timescale indicates that the exposed section spans 13 30 to 7 65 ma the lower middle siwalik boundary occurs at 11 05 ma near the beginning of chron c5n the rate of sediment accumulation increases upsection similar to rate changes previously observed in the pakistan siwalik group and probably in response to increasing proximity of the himalayan thrust belt in the khutia khola section a discordant declination indicates that this region has rotated about a vertical axis 16 6 counterclockwise with respect to the indian subcontinent measurements of 13 c in paleosol carbonate indicate the predominance of c 3 plants until 7 65 ma and the clear presence of c 4 plants higher in the undated portion of the section

a time framework based on magnetostratigraphy for the siwalik sediments of the khaur area northern pakistan the magnetostratigraphy of eleven new sections in the khaur area of northern pakistan is presented all specimens have been subjected to thermal demagnetization the sections taken in adjacent ravines incising the siwalik formations nearly penpendicular to strike form a temporal framework in which to interpret the biological and lithological information a composite section is constructed from several long sections and is correlated to the magnetic polarity time scale chron 6 to chron 15 providing absolute age information for the biostratigraphic zonations of barry et al 1982 detailed sections along the strike of major stratigraphic marker beds document an isochronous horizon and form the basis for paleoenvironmental reconstructions the preservation of a polarity transition in fluvial sediments suggests continuity of sedimentation on a time scale of 103 104 years

coarse sand beach ridges at cowley beach north eastern australia their formative processes and potential as records of tropical cyclone history storm surges generated by tropical cyclones have been considered a primary process for building coarse sand beach ridges along the north eastern queensland coast australia this interpretation has led to the development of palaeotempestology based on the beach ridges to better identify the sedimentary processes responsible for these ridges a high resolution chronostratigraphic analysis of a series of ridges was carried out at cowley beach queensland a meso tidal beach system with a 3 m tide range optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years the ridge crests sit 3 5 to 5 1 m above australian height datum ca mean sea level a ground penetrating radar profile shows two distinct radar facies both of which are dissected by truncation surfaces hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at 2 5 m australian height datum equivalent to the fair weather swash limit during high tide the lower facies comprises a sequence of seaward dipping reflections beach progradation thus occurs via fair weather wave accretion of sand with erosion by storm waves resulting in a sporadic sedimentary record the ridge deposits above the fair weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide the ridges may also include an aeolian component as cyclonic winds can transport beach sand inland especially during low tide and some layers above 2 5 m australian height datum are finer than aeolian ripples found on the backshore coarse sand ridges at cowley beach are thus products of fair weather swash and cyclone inundation modulated by tides knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges this article is protected by copyright all rights reserved

u th age distribution of coral fragments from multiple rubble ridges within the frankland islands great barrier reef implications for past storminess history abstract prograded coral rubble ridges have been widely used as archives for reconstructing long term storm or storminess history chronologies of ridge systems in previous studies are often based on a limited number of low resolution radiocarbon or optically stimulated luminescence osl ages per ridge usually only one age per ridge which carry intrinsic age uncertainties and make interpretation of storm histories problematic to test the fidelity of storm ridges as palaeo storm archives we used high precision u th dating to examine whether different samples from a single ridge are temporally constrained we surveyed three transects of ridge systems from two continental islands normanby island and high island within the frankland islands great barrier reef gbr and obtained 96 u th dates from coral rubble samples collected from within and between different ridges our results revealed significant differences in age ranges between the two islands the steeper and more defined rubble ridges present on normanby island revealed that the majority of u th ages over 60 from a single ridge clustered within a narrow age range 100 years by contrast the lower and less defined ridges on high island which were more likely formed during both storm and non storm high energy events revealed significant scatter in age distribution 200 years with no notable clustering the narrower age ranges obtained from the steeper and more defined rubble ridges suggest that previous approaches of using either limited samples from a single ridge or low precision dating methods to establish chronologies are generally valid at centennial to millennial timescales although caution must be taken to use such approaches for storm history reconstruction on shorter timescales e g decadal the correlation between u th mortality ages of coral rubble and historical stormy periods highlights the possibility of using coral rubble age distribution from rubble ridges to reconstruct the long term regional storminess history u th age distribution of all dated coral rubble samples combined with previously published storm transported coral block data from the same region revealed at least six relatively stormy periods in the past 500 years in the frankland islands region 1570 1590 1760 1780 1800 1830 1860 1880 1940 1960 1980 2010 ce wavelet power analysis of the relative probability of u th age distribution indicates that the pacific decadal oscillation pdo and el nino southern oscillation enso may be partially responsible for the long term variability in storminess

biostratigraphy and geology of the neogene siwalik group of the surai khola and rato khola areas in nepal abstract an almost complete sequence of neogene molasse sediments of the siwalik group in the surai khola khola means small river in nepali area in nepal which was divided into five lithological units includes the upper part of the lower siwaliks the middle and the upper siwaliks it discloses a tectonically uncomplicated southern belt i e the surai khola sequence and a tectonically much disturbed northern belt the upper siwaliks at surai and rato khola yield a rich vertebrate fauna contained within thick bodies of multistoried sandstones the data from the pollen and plant fossils indicate vegetational changes from tropical evergreen forests in the lower and middle siwaliks to dry deciduous forests and grasslands by the beginning of the upper siwaliks biostratigraphically the upper siwalik sediments can be compared with the hexaprotodon sivalensis and the elephas planifrons interval zones of pakistan and with the tatrot and pinjor formations of northwest india palaeomagnetic dating of the surai khola sequence indicate a time scale from 13 to ca 1 million years

reply to the discussion by john nott on coarse sand beach ridges at cowley beach north eastern australia their formative processes and potential as records of tropical cyclone history by tamura et al 2018 sedimentology 65 721 744

magnetic stratigraphy of cenozoic terrestrial sediments and mammalian dispersal the existing literature on the correlation of the magnetic polarity timescale to vertebrate mammalian chronology for the cenozoic is reviewed for all continents except the soviet union the magnetostratigraphic data from north america is the most complete followed by the indian sub continent ten criteria for rating magnetostratigraphic studies are established and the papers reviewed are rated from 1 10 with 10 being the maximum score the timing of mammalian dispersal is examined against the background of information from magnetostratigraphic studies allied with radiometric dating north american land mammal ages are partly defined on immigrant taxa and the boundaries of the nalma are based on dispersal events it has been suggested that dispersal and evolutionary episodes observed in siwalik sediments were correlative to sea level change deduced from delta 18 o data from benthic foraminifera to test this possibility in the general case dispersal events into north america were determined by us

proxy records of holocene storm events in coastal barrier systems storm wave induced markers abstract extreme storm events in the coastal zone are one of the main forcing agents of short term coastal system behavior as such storms represent a major threat to human activities concentrated along the coasts worldwide in order to better understand the frequency of extreme events like storms climate science must rely on longer time records than the century scale records of instrumental weather data proxy records of storm wave or storm wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia this review provides a detailed state of the art compilation of the proxies available from coastal barrier systems to reconstruct holocene storm chronologies paleotempestology the present paper aims i to describe the erosional and depositional processes caused by storm wave action in barrier and back barrier systems i e beach ridges storm scarps and washover deposits ii to understand how storm records can be extracted from barrier and back barrier sedimentary bodies using stratigraphical sedimentological micro paleontological and geochemical proxies and iii to show how to obtain chronological control on past storm events recorded in the sedimentary successions the challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm chronologies using these various proxies are discussed and future research prospects are outlined