magnetic polarity stratigraphy of a plio pleistocene marine sequence of north island new zealand abstract thick sequences of relatively undisturbed plio pleistocene sediments in the wanganui basin north island new zealand consist of well exposed silts clayey silts sandstones rare limestones and several tephras oriented specimens were collected from a section more than 2500 m thick and palaeomagnetic measurements were made using a c demagnetisations in fields up to 35 mt with the aid of tephrochronology the age of the upper sequence is now well established and falls within the matuyama epoch the lower two thirds of the section except for the basal 500 m is predominantly normally magnetised and is interpreted as a very extended sequence of the gauss epoch the lowest 500 m then represents the gilbert epoch the plio pleistocene boundary as defined at vrica italy falls within the upper part of the section studied in the upper nukumaruan stage for the first time a reliable correlation is made with the international boundary using as intermediaries the palaeomagnetic and tephrostratigraphy of deep sea cores from the southwest pacific as a result of the high deposition rate of the order of 1 2 m ky and the apparent lack of unconformities the temporal resolution is high short lived magnetic events are detected especially in the lower matuyama and upper gauss epochs these generally correlate well with events reported from other extended sections

constraints on eustatic sea level changes during the mid pleistocene climate transition evidence from the japanese shallow marine sediment record abstract during the middle pleistocene the nature of glacial interglacial fluctuations changed from low amplitude and a periodicity of 41 ky to high amplitude and quasi periodic of 100 ky the origin of the mid pleistocene climate transition mpt is an unsolved mystery at present there is a debate about whether the initiation of the mpt was a gradual or an abrupt process this study investigated the process of initiation of the mpt from reconstructions of eustatic sea level changes as a proxy for global ice volume based on a reexamination of lithofacies and fossil occurrences from shallow marine sediments omma formation exposed on the west coast of japan the omma formation comprises 19 depositional sequences spanning marine isotope stages mis 56 21 3 reflecting sedimentation under alluvial plain to offshore conditions the data indicate that 1 sea level was lowest during mis 22 0 9 ma 2 sea level during mis 34 1 13 ma and mis 26 0 96 ma was lower than during any other glacial stage except for mis 22 and 3 sea level during mis 22 was at most 20 m lower than during mis 34 and 26 together these findings suggest that the initiation of the mpt was a gradual rather than abrupt process

multi method dating comparison for mid pleistocene rangitawa tephra new zealand abstract the rangitawa tephra a widespread mid pleistocene marker in the new zealand region is dated by fission track thermoluminescence tl infrared stimulated luminescence irsl k ar and single crystal laser fusion sclf 40 ar 39 ar methods as well as by matching to the astronomical timescale via oxygen isotope stratigraphy in deep sea cores fifty one independent numerical age estimates for rangitawa tephra range from 173 to 456 ka however only 15 of these results are considered to be reliable five zircon fission track results four isothermal plateau fission track itpft age estimates on glass shards four sclf 40 ar 39 ar results and two astronomically calibrated age estimates from deep sea cores the weighted mean of the nine reliable fission track age determinations is 345 12 ka in excellent agreement with the weighted mean of 340 7 ka for the two reliable astronomically calibrated age estimates the weighted mean of the four reliable 40 ar 39 ar results 302 8 ka is significantly younger and further ar ar dating is recommended to investigate this difference since the tl and irsl dating methods are experimental for sediments beyond 200 ka we have excluded these from the group of reliable age results tl and irsl results on dunesand appear to be systematically younger than tl results on loess and loess results depend upon analytical procedures

a model for cross shore sediment transport a model for cross shore sediment transport due to random waves is described which adopts a vertically integrated transport description for sheetflow situations the formulation of the transport as a function of the instantaneous velocity field is based on the approach of bailard 1981 this approach assumes in essence that the instantaneous transport is proportional to some power of the instantaneous near bottom velocity implementation of this transport description in a time dependent model requires a formulation of the time mean and some low order moments of the near bottom velocity field an initial formulation based on a monochromatic second order stokes wave representation is presented the model is checked on the basis of both field and laboratory data some consequences for further study are indicated

anomalies in geomagnetic variations on peninsular india near palk strait anomalies in transient geomagnetic variations have been previously studied using data from five permanent observatories in the peninsular india the results from the three observatories falling under the equatorial electrojet showed the presence of a strong current concentration between india and sri lanka island the currents seem to flow at the depth of the crust or upper mantle these findings have been confirmed hereby by collecting data from an array of magnetometers we associate the channelling to the presence of a geological conductor between india and sri lanka island

integrated tephrochronology and magnetostratigraphy for cyclothemic marine strata wanganui basin implications for the pliocene pleistocene boundary in new zealand abstract the middle pliocene to earliest pleistocene part of the rangitikei river section in wanganui basin contains at least six distal tephras five are rhyolitic kowhai eagle hill ohingaiti waipura and vinegar hill tephras and one is andesitic mangamako tephra all tephras occur as macroscopic layers and are enclosed within cyclothemic marine sediments that accumulated in shoreface to outer shelf water depths under conditions of oscillating sea level driven by glacio eustacy the glass and ferromagnesian compositions of the silicic tephras imply derivation from calc alkaline rhyolitic sources either or both of taupo volcanic zone and southern coromandel volcanic zone the waipuru and vinegar hill tephras have isothermal plateau fission track itpft ages of 1 87 0 15 ma and 1 75 0 13 ma respectively paleomagnetic results allow identification of i the gauss matuyama boundary located ca 70 m below the top of the mangaweka mudstone and ii the top of the olduvai subchron placed at the base of the waipuru shellbed the itpft ages of the tephras are consistent with the interpreted magnetostratigraphy and also with astronomically tuned timescales correlation of the rangitikei sequences to the odp site 846 18o record indicates that each sequence corresponds to a glacial interglacial isotope stage couplet and allows ages to be interpolated for tephras not dated directly integration of the new ages for the waipuru and vinegar hill tephras the magnetostratigraphy and the sequence correlations to the astronomically tuned oxygen isotope timescale lead us to place the pliocene pleistocene boundary as defined at the vrica stratotype at the base of the highstand systems tract siltstone of sequence 17 in the rangitikei section 60 m below the vinegar hill tephra

the last glacial maximum in central and southern north island new zealand a paleoenvironmental reconstruction using the kawakawa tephra formation as a chronostratigraphic marker abstract kawakawa tephra formation comprising oruanui ignimbrite flow member and aokautere ash airfall member represents the products of an exceptionally large and widespread volcanic eruption from taupo volcanic centre in the north island of new zealand the eruption occurred during the last glacial maximum and is radiocarbon dated at c 22 6 ka b p thermoluminescence ages are in broad agreement with the radiocarbon age the presence of aokautere ash in loess deposits in alluvial gully fills on river terraces and its absence from unstable sites permits a detailed assessment of geomorphic activity during the last glacial maximum widespread erosion of regolith aggradation of river valleys and deposition of loess particularly in the period following eruption of the kawakawa point to a cold dry variable climate a collation of pollen data for sediments containing aokautere ash and those 14c dated in the range 17 23 ka shows that tall forest was highly restricted in the central and southern parts of the north island an apparently subalpine grassland shrubland was present at sites from present sea level to over 800 m elevation suggesting that factors other than lower temperatures such as exposure to wind and frost fire and reduced rainfall were important in controlling vegetation patterns we conclude that the interval 23 13 ka b p broadly equivalent to oxygen isotope stage 2 represents the period of greatest environmental change in the north island

constraints on the amplitude of late pliocene eustatic sea level fluctuations new evidence from the new zealand shallow marine sediment record since 2 5 ma global eustatic sea level fluctuations have driven recurrent transgressions and regressions of the shoreline across the world9s continental shelves the resulting shallow marine sedimentary record is cyclothemic each cyclothem corresponding to a single milankovitch climatic or sea level cycle wanganui basin new zealand contains one of the most complete late neogene shallow marine stratigraphic records in the world in the form of a continuous cyclostratigraphy representing every 41 k y and 100 k y sea level cycle since oxygen isotope stage 104 ca 2 6 ma a eustatic sea level curve is derived for oxygen isotope stages 100 74 from high resolution faunal paleobathymetric subsidence and stratigraphic analyses of 12 superposed shallow marine cyclothems in the rangitikei river section wanganui basin between 2 6 and 2 0 ma minimum amplitudes of eustatic sea level fluctuations ranged from 110 20 m stages 100 99 to 25 10 m stages 76 75 these independently derived fluctuations are 20 larger than previous estimates and imply greater climatic variability during the onset of major northern hemisphere ice ages

morphodynamic modelling for a tidal inlet in the wadden sea abstract a dynamic model for morphological development in a tidal inlet het friesche zeegat in the wadden sea along the northern coast of the netherlands is set up to obtain a better understanding of the behaviour of the morphological system around tidal inlets the model is based on delmor a program package for morphological changes developed at delft hydraulics computations of the flow the sediment transport the initial bed level change rate as well as long term morphological development have been carried out the model has proven to be a useful research tool even though it does not yet reproduce reality in detail

sea level and climate signatures recorded in orbitally forced continental margin deposits over the last 1 myr new perspectives from the bohai sea abstract sediment accumulation in continental margins during the quaternary period was substantially influenced by both sea level fluctuations and climate changes however the response of sediment accumulation to these changes on an orbital timescale remains poorly understood for two main reasons the scarcity of sedimentary records with a high resolution chronology and the difficulty in distinguishing the role of sea level from regional climate signals here we present the results of sediment color reflectance c grain size and total organic carbon toc content of core bh08 212 4 m in length spanning the last 1 myr recovered from the bohai sea china the chronology of core bh08 on the orbital timescale is constrained by both magnetostratigraphy and astronomical tuning sedimentary facies analysis suggests that the sedimentary sequence is dominated by the alternation of a deltaic system and floodplain deposition principal components analysis of the grain size data reveals two principal components pcs including pc1 reflecting the 31 500 m fraction and pc2 reflecting the 18 66 m fraction comparison of sample scores on pc1 pc2 and c with the alternation of sedimentary environments reveals that pc1 and c reflect cycles of deltaic and floodplain deposition at 100 kyr and 40 kyr periodicities while pc2 exhibits a 20 kyr periodicity in addition to the 100 kyr and 40 kyr cycles we infer that pc1 and c are mainly sea level dependent whereas pc2 is controlled by the combination of changes in monsoon climate and sea level we suggest that milankovitch scale monsoon climate fluctuations controlled the sediments supply to the bohai sea during the last 1 myr while the redistribution of sediments by marine processes e g tidal currents has partially obscured the monsoonal signal in the grain size proxy e g pc1 which instead is sensitive to sea level change our results provide an example of the influence of climate and sea level on sediment accumulation in a shallow continental margin setting influenced by monsoonal climate in an icehouse world

the evolution of the east coast of india abstract the evolution of the east coast of india from the permian up to the end of the cretaceous is traced peninsular india had an imprint of hercynian epeirogeny manifested in the formation of some regional geofracture and rift systems the east coast basins mahanadi godavari krishna palar and cauvery basins are pericratonic the structural style and regional trends during the jurassic are ne sw the basin architecture during the late jurassic is of horst graben type the close of the mesozoic was marked by regional easterly regression basinal tilt and formation of monoclinal post mesozoic sedimentary cover the oldest sequence in these basins is of permian age and is known in the palar basin the triassic sediments are not known in the land area from the faunistic and floristic evidence the uppermost jurassic lower cretaceous gondwana sediments are paralic the occurrence of marine permian palynofossils in the indian east coast sediments points to the presence of a narrow paleo shelf to the east prior to the break up and drift of gondwanaland different continental fits offered by various authors are analysed to understand the evolution of the indian ocean the structural grain and basin architecture of the pre drift and post drift basins of the east coast of india are similar to that of the western and northwestern coastal basins of australia it is postulated that permian sediments were extensive and have since been eroded such a pattern of erosion of permian beds is also observed in northwestern australia the most favoured fit of western australia against northern india does not conform to the regional geotectonic pattern and the nature of sediments that are present in india and the australian counterparts in addition to geological evidence palaeo biological evidence has been considered which favours the juxtaposition of the east coast of india with western australia the authors are of the opinion that palaeomagnetic interpretations which have of late gained importance fail to explain the pre drift geological similarities of the east coast of india and western coast of australia

pleistocene reef development in the southwest ryukyu islands japan abstract calcareous nannofossil and sedimentological studies of the pleistocene ryukyu group based on 13 cores and surface outcrops on irabu jima and shimoji jima the ryukyu islands southwestern japan suggest that these sediments were deposited at 1 5 0 3 ma and unconformably overlie the pliocene shimajiri group the ryukyu group consists mainly of reef complex deposits which accumulated in a wide range of depositional environments from shallow reef flat to deep insular shelf carbonate lithofacies representing 10 depositional environments were delineated by comparison with the present day marine sediments and biota around the ryukyus five coral assemblages were defined by species composition and the morphology of fossil forms within the coral limestone each indicating a particular environment the ryukyu group in the study area is composed of 13 lithologic units a complete succession of units commences with coral limestone lst or tst grading upward into rhodolith and larger foraminiferal limestones tst overlain by coral limestone hst episodic subaerial exposure and subordinate karstification commonly occurred after deposition the study area subsided during the deposition of units 1 12 and then was uplifted during deposition of unit 13 reef development may have been dominated by obliquity or precessional cycles sixth and seventh order cycles respectively for the first 0 5 million years 1 5 1 ma after which it may have responded to fifth order eccentricity cycles

toward a comprehensive upper quaternary tephra and ignimbrite stratigraphy in new zealand using electron microprobe analysis of glass shards abstract new zealand quaternary marine and terrestrial sequences contain numerous tephras or volcanic ash horizons that are the distal correlatives of voluminous welded ignimbrite sheets erupted from central north island electron microprobe analyses of glass shards from the distal tephras demonstrate their homogeneity and are shown to identify each tephra examined by matching tephras from stratigraphically controlled sequences the first comprehensive tephra stratigraphy spanning from 50 000 to 700 000 yr ago and covering the new zealand region is advanced analyses on glass shards from the unwelded base of ignimbrite sheets are comparable to the distal tephra analyses and allow correlation between ignimbrites and to the distal tephras the better exposed tephra record constrains the number of separate eruptive events and the stratigraphy of the ignimbrites both of which were previously confused by lack of outcrop samples from pumiceous marine sediments were found to contain two or more chemically distinct populations of glass the pumice is in cross bedded sands or sand lenses within conglomerate attesting to a shallow high energy environment where reworking could occur however each glass population could be matched to older known tephras

tidal inlet sediment bypassing at mixed energy barrier islands abstract the large scale littoral sediment drift along barrier island coasts involves alongshore sand transport at the islands surf zone and across tidal inlets mechanisms of sediment bypassing at non migrating mixed energy tidal inlets are discussed based on process based numerical modeling of sediment dynamics at an exemplary barrier island system in the southern north sea residual transport pathways of distinct sediment grain size fractions and morphological changes reveal the complexity of processes at tidal inlets driven by the non linear interaction of competing tidal and wave forces sediment bypassing from the updrift to the downdrift shoreline of a tidal inlet is evaluated and the ratio of bypassed to recirculated sand volumes is estimated common inlet bypassing schemes are discussed and verified it is shown that the different bypassing mechanisms can happen simultaneously and are related to the transport behavior of particular sediment grain size fractions very fine to fine sand bypasses the inlet along the entire ebb tidal delta periphery by wave induced transport processes fine to medium sand is transported by the ebb directed tidal currents in the inlet throat to the ebb tidal delta where wave driven transport processes and bar welding bypasses the sediments to the downdrift shore for fine to medium and medium sands a sediment recirculation cell at the downdrift ebb tidal delta and reversal to the main inlet throat is identified

the 18 6 yr nodal cycle and its impact on tidal sedimentation abstract the 18 6 yr nodal cycle modulates tidal amplitudes and currents and consequently sedimentation in tide influenced sedimentary environments data are presented which show that such effects are obvious along the coast of the dutch barrier islands and in the sedimentary fill of abandoned channels

mechanics and rates of tidal inlet migration modeling and application to natural examples tidal inlets on barrier coasts can migrate alongshore hundreds of meters per year often presenting great management and engineering challenges here we perform model experiments with migrating tidal inlets in delft3d swan to investigate the mechanics and rates of inlet migration model experiments with obliquely approaching waves suggest that tidal inlet migration occurs due to three mechanisms 1 littoral sediment deposition along the updrift inlet bank 2 wave driven sediment transport preferentially eroding the downdrift bank of the inlet and 3 flood tide driven flow preferentially cutting along the downdrift inlet bank because it is less obstructed by flood tidal delta deposits to quantify tidal inlet migration we propose and apply a simple mass balance framework of sediment fluxes around inlets that includes alongshore sediment bypassing and flood tidal delta deposition in model experiments both updrift littoral sediment and the eroded downdrift inlet bank are sediment sources to the growing updrift barrier and the flood tidal delta such that tidal inlets can be net sink of up to 150 of the littoral sediment flux our mass balance framework demonstrates how with flood tidal deltas acting as a littoral sediment sink migrating tidal inlets can drive erosion of the downdrift barrier beach parameterizing model experiments we propose a predictive model of tidal inlet migration rates based upon the relative momentum flux of the inlet jet and the alongshore radiation stress we then compare these predicted migration rates to 22 natural tidal inlets along the u s east coast and find good agreement

early to middle pleistocene tephrochronology of north island new zealand implications for volcanism tectonism and paleoenvironments thick volcaniclastic sequences of early to middle pleistocene age in southern north island new zealand contain rhyolitic tephra beds that record the early history of the taupo volcanic zone tvz at least 54 different tephra beds are recorded and their chronology is defined by glass fission track ages and paleomagnetism the tephra beds span the interval ca 2 0 0 6 ma and provide an event frequency of 1 19 k y significantly higher than the frequency of sheet forming ignimbrites preserved in the tvz at this time 1 100 k y the distal tephra beds thus provide a record of volcanism not revealed in the proximal volcanic region and suggest a major period of explosive activity at ca 1 79 1 60 ma several important marker horizons are identified pakihikura tephra 1 63 ma mangatewaiiti tephra 1 24 ma potaka tephra 1 00 ma kidnappers b tephra 1 00 ma and kaukatea tephra 0 88 ma these tephra beds allow direct correlation between 1 marine and nonmarine facies and 2 the fore arc and back arc regions of new zealand the tephra beds provide a framework for a paleoenvironmental reconstruction of the southern north island volcaniclastic transport routes from the tvz to basins in the south and southeast and through the site of present mountain ranges supplied material to a terrestrial lowland fore arc area in the interval 1 64 0 7 ma uplift and deformation since 0 7 ma have disrupted paleodrainage routes diverting them to the north and southwest

the stratigraphic architecture of late pliocene 2 8 2 4 ma asymmetrical shelf sequences western wanganui basin new zealand abstract the western wanganui basin in the vicinity of parikino contains a 410 m thick succession of thirteen sequences that accumulated between 2 8 and 2 4 ma traditional facies analysis of the succession indicates accumulation of the sequences in shoreface to mid shelf depositional palaeoenvironments the late pliocene sequences have been correlated with oxygen isotope stages g10 to g92 and each of 41 ka glacial interglacial stage couplets is represented by an individual depositional sequence comprising transgressive tst highstand hst and regressive rst systems tracts most sequence boundaries are unconformable and coincide with transgressive surfaces of erosion tse ravinement surface with ophiomorpha burrows extending down into underlying sandstone one sequence boundary at the base of the wilkies shellbed is a correlative conformity two types of shellbed occur within tsts and are associated with key sequence stratigraphic surfaces onlap and backlap shellbed onlap shellbeds onlap the tse and sequence boundary backlap shellbeds result from stratigraphic condensation at the top of the tst and are overlain by the downlap surface dls in most of the sequences the onlap and backlap shellbeds are superposed forming compound shellbeds rarely a downlap shellbed overlies the dls within the base of hsts hsts are composed typically of massive aggradational mid shelf siltstone that grades up into sandstone which forms thick progradational inner shelf to shoreface lithofacies attributed to regressive systems tracts rst lensoidal toplap shellbeds comprised of reworked nearshore storm emplaced fauna occur within the upper part of rsts all of the parikino sequences have asymmetrical architectures with thin tsts this arises because of the very low rates of non tropical carbonate accumulation during the transgressions that is about half of the 41 ka period of each cycle amounting to a few metres at most of shellbed followed by very high rates of terrigenous sediment accumulation during the latter half of cycles an implication of this work is that marked 40 60 m eustatic sea level changes occurred repeatedly during the interval 2 8 to 2 4 ma this implies substantial and successive continental glaciations from at least 2 8 ma probably in the northern hemisphere

short period geomagnetic variations at two stations in sri lanka and their relation to channelling of induced currents through a conducting region beneath the palk strait abstract electric currents induced in the deep ocean and channelled through a conducting region beneath the palk strait have been invoked by earlier workers to explain anomalies in transient geomagnetic variations such as bays sscs and substorms observed at some south indian coastal stations the need for confirmation of this idea by measurement on the sri lankan side across the palk strait has been emphasised by these workers in the present study rates of change in the geomagnetic field components in the period range 20 600 s recorded at kondavil and hikkaduwa two stations in the equatorial electrojet belt near the northern and southwestern coasts respectively of sri lanka have been analysed and discussed the results are presented in the form of variation with period of z h and d h at kondavil z h at hikkaduwa and of hc hh the ratio of h components at colombo and hikkaduwa they provide strong confirmatory evidence for channelling of induced currents through a conducting region beneath the palk strait and could serve as valuable control data in any detailed modelling of the conductivity structure beneath the palk strait a day time enhancement of z h at hikkaduwa at all periods in the observed range and a similar enhancement of hc hh were observed these enhancements are possibly due to the effect of the equatorial electrojet on the short period variations

basin physiography and tectonic influence on sequence architecture and stacking pattern pleistocene succession of the canoa basin central ecuador facies shell bed features and sequence stratigraphic framework for the shallow marine pleistocene upper canoa and tablazo formations are presented based on outcrop data from the southern coast of cabo san lorenzo ecuador sediments of this succession exhibit a distinct cyclic pattern consisting of a stack of eight depositional sequences cyclothems likely developed under the main control of orbitally induced sea level changes as a rule within the studied interval an idealized cyclothem is composed of a transgressive systems tract tst and a highstand systems tract hst whereas deposits attributable to the lowstand and falling stage systems tracts are not present transgressive lithosomes may be defined by estuarine deposits interposed between the sequence boundary and the ravinement surface back barrier wedge and by upward fining shoreface to inner shelf facies successions above the ravinement backstepping shelf wedge separated by an expanded siliciclastic core hiatal shell concentrations occur at the base onlap shell beds and the top backlap shell beds of the transgressive shelf wedges and some occur at the base of highstand systems tracts downlap shell beds on the basis of sedimentary facies geometry taphonomy and paleoecology of shell beds and the nature of the transition between siliciclastic and mollusk bearing sediments cyclothems were classified into two main types that show dependence upon paleoshoreline morphological configuration sheltered in the upper canoa formation and exposed in the tablazo formation notwithstanding the different synsedimentary tectonic and climatic regimes the ecuadorian cyclothems share basic patterns of condensation and facies assemblages with other roughly coeval cyclothemic successions around the world this suggests that 1 hiatal shell bed development is not just a temperate latitude phenomenon 2 a global process such as glacio eustatic sea level change is the primary mechanism of control for the general architecture of sequences and 3 specific paleogeographic settings play an important role by determining the taphonomic and paleoecologic characteristics of key shell beds the nature of their contacts with the encasing sediments and the type of the component set of facies at a multicycle time scale tectonics influenced the long term trend of the relative sea level changes and consequently the large scale stratigraphic organization owing to the continued tectonic uplift of the area successive high frequency depositional sequences are nested to form a longer order falling stage sequence set

induction models of southern india and the effect of off shore geology abstract simple numerical tests based on thin sheet modelling are used to define the conductors most probably responsible for current channelling in the region including southern india a combination of crustal conductors located in the indo ceylon graben and underneath the comorin ridge best reproduces the observations at periods of 50 100 min in so far as channelling is concerned daytime variations do not help to define the location of conductors any better than night time data and may thus be ignored

late pleistocene sea level oscillations mis 10 2 recorded in shallow marine and coastal plain sediments of the southern wanganui basin new zealand abstract the northern wanganui basin new zealand is one of the key global sites for understanding marine cyclic sedimentation during the quaternary this paper presents the first evidence of marine cyclic sedimentation from its central southern parts sedimentological micropalaeontological and palynological analyses on a 280 m deep borehole encountered units dating back to mis 10 the sequence includes four marine cycles spanning mis 9 5 which are overlain by terrestrial fluvial aggradation surfaces dating from mis 4 2 each marine unit represents a progressively shallowing depositional environment from the mid shelf to coastal plain this is overlain by a terrestrial sequence of lowstand fluvial terraces localized fault movements appear to have influenced the sedimentary character of the sequence during mis 7a and 5e producing basement highs which provided protection to the shoreline the cyclothems described in this paper now extend the already extensive previously described record from mis 17 10 to produce a combined eustatic record of quaternary sea level change within the basin to mis 5 they also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space

characterizing earthquake recurrence parameters for offshore faults in the low strain compressional kapiti manawatu fault system new zealand 1 seafloor fault scarps and near surface deformation of late quaternary seismic reflectors occur along the eastern margin of the wanganui basin 200 km behind the active hikurangi subduction front southern north island new zealand the offshore scarps are associated with the low strain compressional kapiti manawatu fault system kmfs which comprises high angle 60 reactivated reverse and normal faults oriented ne sw highly oblique to the coast seafloor scarps range from 10 m high and moderate to long fault seafloor rupture lengths and those in central parts of the fault system are characterized by low scarps 10 000 a suggest that the seismic hazard of the kapiti manawatu region is relatively low incorporation of these new geological data however is likely to increase slightly the expected seismic hazard in southern north island the method of determining the earthquake recurrence parameters of offshore faults has potentially wider applications elsewhere

pleistocene unconformity bounded shelf sequences wanganui basin new zealand correlated with global isotope record abstract eleven successive unconformity bound sequences in the castlecliff section wanganui basin each typically composed of a lower variably conglomeratic 0 1 2 m thick shell bed and an upper 5 20 m thick barren siltstone are identified in the stratotype of the local new zealand middle pleistocene castlecliffian stage based on magnetostratigraphy the section is correlated with the published benthonic oxygen isotope curve for dsdp core 552a from the north atlantic each of the sequences accumulated during one of the odd numbered interglacial isotope stages in the interval 31 to 11 inclusive the unconformities developed during intervening glacial ages when the shelf was exposed through glacio eustatic lowering the correlation provides a geochronologic framework for assessment of the eustatic contribution to the generation of the sequences in a situation where the paleoshorelines and related shelf sequences are preserved and for which an independent approximation of the sea level history is available in the form of an oxygen isotope curve

can multiple tidal inlets be stable abstract the gorge stability of inlets connecting the same bay to the ocean is analysed the basic premise is that when the tidal maximum of the bottom shear stress in an inlet is larger than the equilibrium shear the inlet is in a scouring mode and when smaller than the equilibrium shear stress the inlet is in a shoaling mode the tidal maximum of the bottom shear stress equals the equilibrium shear stress when the inlet is in equilibrium with the hydraulic environment an inlet is called stable when after a small change the cross sectional area returns to its equilibrium value using a linearized lumped parameter model for the flow in the inlets it is shown that for a two inlet bay system neither of the two inlets can be stable this implies that when assuming the inlets to be in equilibrium with the hydraulic environment a small change in the cross sectional area of one or both of the inlets will result in the closure of one or both of the inlets starting with the results for the two inlet bay system arguments are presented that suggest a similar conclusion holds for multiple inlets i e ultimately all inlets will close or at best one will remain open

upper quaternary marine terrace chronology and deformation south taranaki new zealand an extensive flight of late quaternary marine terraces in the south taranaki region of the north island of new zealand is dated using fission track radiocarbon and amino acid racemization methods a simple model of terrace deformation based on a doming type uplift pattern allows terrace strandline ages to be estimated twelve strandlines are recognized and are estimated to have formed during high sea level stands at 60 000 80 000 100 000 120 000 135 000 210 000 310 000 340 000 400 000 450 000 520 000 600 000 and 680 000 yr b p

astronomic timescale for the pliocene atlantic δ18o and dust flux records of ocean drilling program site 659 high resolution benthic oxygen isotope and dust flux records from ocean drilling program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the atlantic from 2 85 ma back to 5 ma spectral analysis of the 18o record indicates that the 41 kyr period of earth s orbital obliquity dominates the pliocene record this is shown to be true regardless of fundamental changes in the earth s climate during the pliocene however the cycles of sahelian aridity fluctuations indicate a shift in spectral character near 3 ma from the early pliocene to 3 ma the periodicities were dominantly precessional 19 and 23 kyr and remained strong until 1 5 ma subsequent to 3 ma the variance at the obliquity period 41 kyr increased the timescale tuned to precession suggests that the pliocene was longer than previously estimated by more than 0 5 m y

zircon fission track age for middle pleistocene rangitawa tephra new zealand stratigraphic and paleoclimatic significance rangitawa tephra is an important stratigraphic marker in mid pleistocene marine and terrestrial sequences in new zealand and adjacent ocean basins zircon fission track ages zfta on rangitawa tephra from five sites in the southern north island yield mean site ages in the range 0 34 to 0 40 ma with a weighted mean of 0 35 0 04 ma 1 on the basis of glass shard major element chemistry ferromagnesian mineralogy zfta and similarity of paleomagnetic dates of proposed tephra correlatives in deep sea cores it is concluded that rangitawa tephra represents a major eruptive event in the taupo volcanic zone most probably associated with eruption of the whakamaru group ignimbrites 0 35 0 39 ma or less likely the paeroa range group ignimbrites 0 36 0 38 ma pollen analyses from two onshore sites together with regional loess stratigraphy show that rangitawa tephra was erupted during a glacial period the zfta and previously reported oxygen isotope data from dsdp site 594 indicate that rangitawa tephra was erupted near the end of oxygen isotope stage 10

controls on active forearc basin stratigraphy and sediment fluxes the pleistocene of hawke bay new zealand detailed high resolution documentation of forearc basin fi ll is scarce in the literature in this geological and geophysical study we investigated the pleistocene sedimentary record of the tectonically active hawke bay forearc domain of the hikurangi subduction margin of new zealand interpretation of an extensive seismic refl ection data set that is correlated with marine cores and onshore geological maps identifi es the detailed stratigraphic architecture of the last 1 1 m y this analysis reveals the infl uences and interactions of tectonic deformation climate eustasy and isostasy on forearc basin sedimentation eleven 100 k y depositional sequences are recognized in the basin fi ll thus highlighting the dominance of pleistocene climate eustasy on sequence development the stacking pattern and isopach maps of sequences exhibit an overall retrogradational trend and an arcward migration of depocenters these trends progressively develop a basinwide diachronous and composite erosion unconformity formed by the lateral succession and landward encroachment of the 12 sequence bounding unconformities s12 to s1 among these the s5 surface ca 430 ka is an angular unconformity that separates major megasequences of the sedimentary record the forearc domain evolved from a series of ridge parallel basins to a succession of connected basins that have progressively developed around major growing thrust faulted ridges since ca 430 ka this change in basin confi guration and associated signifi cant increase of the preserved sediment fluxes occurred synchronous with the reactivation of major out of sequence thrusts and the completion of the mid pleistocene transition

application of ridge regression in inversion of low latitude magnetic anomalies derived from space measurements abstract anomalies in total field horizontal and vertical components over the indian region derived from magsat measurements have been inverted through the ridge regression method basically to test 1 the application of the method in deriving a stable estimate of crustal magnetisation and 2 the relative amount of information on crustal magnetisation contained in scalar vis a vis vector data results show that the instabilities in magnetisation solution that appear when mayhew s conventional method is applied in low latitudes could be removed through the ridge regression technique it was also noticed that magnetisation distribution estimated through the inversion of the total field b does not relate well with the geological features in the equatorial region inversion of thez anomaly alone gives realistic results for the equatorial region but not over higher latitudes we conclude that a joint inversion ofx andz anomalies provides a magnetisation estimate consistent with known geological features both for equatorial and higher latitudes

chronology of pliocene and quaternary bioevents and climatic events from fission track ages on tephra beds wairarapa new zealand abstract high resolution pliocene and pleistocene sequences exposed on land in new zealand are some of the few detailed records of widepread marine bioevents and paleoclimatic changes in the southern hemisphere marine biostratigraphy calibrated in deep sea cores by paleomagnetic reversals has been the primary basis for the chronology of these sequences we have determined ages for several tephra beds which now provide an independent numerical age calibration for a well studied marine and terrestrial section in wairarapa by using the isothermal plateau fission track itpft method on volcanic glass we have overcome the problems of partial track fading and detrital mineral contamination which hindered earlier studies to reveal a new chronology extending back to nearly 5 ma our ages for the hikawera tuff 4 91 0 25 ma and spooner tuff 3 44 0 13 ma are consistent with the appearance and disappearance of many early pliocene foraminiferial species validating their age calibration in new zealand however some fossil occurrences including coccoliths differ temporally by as much as 0 55 ma perhaps due to local tectonic induced recycling four pleistocene tephra beds potaka tephra 1 00 0 03 ma kaukatea tephra 0 87 0 05 ma rangitawa tephra ca 0 35 ma and kawakawa tephra ca 0 22 ma are now recognised in the wairarapa sequence via stratigraphic and new geochemical and age data these beds allow direct correlation to other marine and terrestrial basins as well as volcanic regions in new zealand and will ultimately aid in a regional paleoenvironmental reconstruction where bioevents are absent the tephra ages indicate that the marine sediment accumulation rates varied from 90 to 250 m ma between different sections of the pliocene and reached ca 350 m ma in the last 2 4 ma when the sequence displays pronounced glacioeustatic cyclic deposition in the terrestrial realm the oldest loess in new zealand is now constrained to between 1 00 and 0 87 ma

long term slip rates and fault interactions under low contractional strain wanganui basin new zealand the newly mapped kapiti manawatu fault system kmfs in southern north island new zealand accommodated 3 5 km of basement throw over the last 3 myr along strike throw profiles are generated using seven stratigraphic markers interpreted from seismic reflection profiles acquired 3 km apart the profiles are symmetrical about their point of maximum displacement and cumulative profiles suggest that the reverse fault system behaves coherently the kmfs originates from the reactivation of extensional structures with fault lengths remaining constant over time contractional deformation started at circa 1750 400 ka maximum dip slip rates along individual faults are 1 77 0 53 and 0 74 0 22 mm yr 1 for the 0 120 and 120 1350 ka periods respectively the maximum cumulative throw rates across the kmfs are 4 9 1 5 and 1 5 0 5 mm yr 1 for the same periods long term strain rates across the kmfs are 2 5 times smaller than strain rates in the forearc basin of the hikurangi subduction margin located less than 100 km to the east the faults of the kmfs may extend to depth and link with the subducted pacific plate

a morphological behaviour model for the outer delta of mixed energy tidal inlets abstract the long term evolution of the seaward part of mixed energy tidal inlet systems is analysed and modelled mathematically in terms of aggregated morphological parameters the model is an adapted version of a two line model in which empirical information on the equilibrium state of the outer delta is included thus detailed computations of the water and sediment motion at the hydrodynamic time scale are avoided the viability of the concept is tested and the model is verified against data from one of the inlets of the western wadden sea the results of a number of practice based applications are shown and discussed

new zealand quaternary stratigraphy an overview abstract new zealand quaternary strata including marine sediments loess volcanic and glacial deposits offer detailed records of quaternary environmental change from a geographically significant location time stratigraphic subdivision of new zealand quaternary strata based on marine biostratigraphy and climatostratigraphy has resulted in a series of locally defined stages and substages the plio pleistocene boundary as defined at vrica in italy and dated at ca 1 63 ma lies near the top of the nukumaruan stage in new zealand the first faunal evidence of cooling in new zealand plio pleistocene sequences occurs much earlier at the base of the nukumaruan stage ca 2 4 ma with the appearance in central new zealand of the subantarctic taxa chlamys delicatula and jacquinotia edwardsii although glacial deposits of the south island have long been central to new zealand quaternary stratigraphy they are poorly dated and lack continuity more complete records of quaternary events are found within uplifted marine strata and associated terrestrial deposits of the north island such as in wanganui basin the use of widespread rhyolite tephra for precise correlation and dating in north island offers much for improved land sea correlations direct correlation of on land sequences using tephra with oxygen isotope stages of deep sea cores may negate the need for further local time stratigraphic subdivision in the new zealand quaternary however there will still be scope for regional comparisons highlighting climatic changes not apparent in deep sea cores

evaluation of the relative roles of global versus local sedimentary controls on middle to late pleistocene formation of continental margin strata canterbury basin new zealand determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy in this paper the relative contribution of these factors on continental margin evolution during the middle to late pleistocene is evaluated using samples from integrated ocean drilling program expedition 317 core logging biostratigraphy and quantitative x ray diffraction mineralogy are used to delineate continental shelf sedimentary systems major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of middle to upper pleistocene sequences however a preliminary chronology suggests that sequence boundary formation cannot be linked one to one with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles smaller amplitude higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply their stratigraphy is variable in time and across the shelf suggesting a strong influence of local sedimentary forcing in their formation changes in sediment composition after the middle pleistocene transition indicate that sediment transfer from onshore sources in the glaciated southern alps to the middle shelf occurred over a single 100 ka glacio eustatic cycle with an additional 100 ka lag before the mineralogical signal was preserved on the outer shelf this phenomenon is coincident with rapid shelf progradation in this basin suggesting a causal relation between across shelf sediment transport and margin progradation this is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the middle to late pleistocene this work shows that compositional changes in mud dominated successions can lead to a sequence stratigraphic interpretation and the identification of high frequency sequences which may not be possible using a conventional stratigraphic approach

the interpretation of magnetometer array studies summary two dimensional arrays of three component magnetometers have introduced a new geophysical technique useful in the study of the upper mantle and crust particularly in tectonically active regions sources of incident magnetic fields include geomagnetic substorms and the daily variation methods and difficulties in interpretation are discussed in the light of the first five years use of magnetometer arrays maps of fourier transform coefficients assist qualitative interpretation but differ from other geophysical anomaly maps in combining the source field and the response of the earth for quantitative interpretation the normal source and anomalous response fields must be separated methods of separation and their limitations are considered numerical modelling of structures to fit normalized anomalous fields for two dimensional geometries of conductors and fields is successful in some cases in others although the variation field anomaly and the current system are long and narrow the behaviour is not two dimensional because the regions of induction are distant and or of unknown shape such current concentration anomalies are common in the crust and can give rise to very large anomalies in cases where the conductive geometry is complicated and not even crudely two dimensional fourier transform anomaly maps are not very useful as their features are extremely variable probably because of interference of the anomalous fields in such cases transfer functions may prove helpful development of three dimensional numerical modelling has started but is cost limited at the present stage

palynology of oxygen isotope stage 6 and substage 5e from the cover beds of a marine terrace taranaki new zealand abstract cover beds on uplifted quaternary marine terraces in the taranaki wanganui area of new zealand include organic deposits which yield abundant pollen in the west at ohawe marine shore platform deposits are overlain by laterally extensive lignites and laharic breccia interbedded with alluvium and capped by tephra rich loess following a time of presumably interglacial marine deposition on the platform a long period of glacial climate is suggested by pollen floras dominated by grass and shrubland taxa trees were sparse but the abundance of podocarps nothofagus and tree ferns increased during at least one interval suggesting minor climatic amelioration near the top of the section a major change in regional vegetation is recorded by a dominance of pollen derived from podocarp hardwood forest taxa including ascarina interpreted as indicating a fully interglacial climate the marine platform previously assigned to oxygen isotope substage 5e is now placed in stage 7 the overlying deposits were deposited during glacial stage 6 while interglacial substage 5e is recorded by sediment and pollen assemblages near the top of the section

a review of wanganui basin new zealand global reference section for shallow marine plio pleistocene 2 5 0 ma cyclostratigraphy abstract wanganui basin new zealand contains one of the most complete late neogene marine stratigraphic records in the world the ca 2 km thick basin fill for the last ca 2 5 ma comprises 47 superposed cyclothems which correspond to successive 5th 100 ka and 6th 41 ka order glacio eustatic sea level fluctuations on the palaeo new zealand shelf since oxygen isotope stage 100 stages 100 to 5 are represented by marine cyclothems whereas stages 17 to 3 are represented by a suite of coeval and younger uplifted marine terrace sequences additionally a predominantly glacial loess stratigraphy exists for isotope stages 12 2 the presence of interbedded tephras and an established paleomagnetic stratigraphy allows the development of an integrated cyclostratigraphy for wanganui basin which correlates closely with the global oxygen isotope scale in all except two cases cycles 12 and 36 individual unconformity bound cyclothems sequences represent a single glacial interglacial couplet of milankovitch frequency lithologic and faunal variation within the cyclothems corresponds closely to that predicted by the sequence stratigraphic model each cyclothem generally contains a transgressive systems tract a mid cycle condensed shellbed a highstand systems tract and often a regressive systems tract six common cyclothem motifs are inferred to represent deposition in shelf locations between the highstand and lowstand shorelines viz the hawera maxwell turakina seafield castlecliff and rangitikei motifs a seventh type the nukumaru motif includes coquina limestone and represents deposition in shoreface and very shallow water marine environments

palaeoenvironment and biogeography of a late mis 3 fossil beetle fauna from south taranaki new zealand fossil beetles from a last glacial landslide generated lake forest sequence aged 33 480 34 410 cal yr bp late marine isotope stage 3 mis 3 are identified from the waitotara valley in south taranaki north island new zealand the stratigraphy indicates that the landslide caused changes to local hydrology resulting in the formation of a lake swamp environment and subsequent transition to forest fossil leaves suggest a forest dominated by nothofagus menziesii and radiocarbon ages indicate the site was forested for around 4000 yr a fossil beetle based temperature estimate using the maximum likelihood envelope method indicates the climate was cooler than present day the distributions of the fossil beetle taxa are examined and compared with the modern ecological patterns the fossil fauna is very typical of a modern day nelson northern south island fauna none of the beetle species is present in the modern south taranaki fauna and many taxa such as platypus caviceps alema paradoxa rhyzobius consors syrphetodes ater cyclaxyra impressa and species of grynoma and pycnomerus are now absent from part or all of the lower north island this is important because the lower north island is currently an area of low diversity and endemism and these results suggest this biogeographical pattern stems from the last glaciation copyright 2008 john wiley sons ltd

depth of the conductosphere under the indian shield abstract the depth at which the highly conducting layer of the upper mantle the conductosphere begins under the indian shield is estimated to do this the geomagnetic daily variations measured north of the magnetic equator are separated into contributions of internal and external origin and from the latter an analytical representation for the ionospheric current system is inferred the external field produced by this current and the field induced by it in a two layer conductivity model of the earth consisting of an insulator overlying a perfect conductor are obtained the total field thus calculated is compared with the data to obtain the conductosphere depth the conductosphere below the indian shield is found to be located at approximately 1000 km well below the average global value in agreement with previous findings below the african shield this result supports the hypothesis that there is a correlation between the deep conducting structure of the earth and some tectonic features

magnetometer array studies earth structure and tectonic processes this review presents results from magnetovariation fields recorded by two dimensional arrays of magnetometers the emphasis is on the conductive structures mapped and studied and their tectonic implications eleven arrays were operated in north america between 1967 and 1985 a region of highly conductive uppermost mantle and or lower crust extending at least from 33 n to 54 n has been shown to extend beneath much of the continent west of the rocky mountains two recent investigations are discussed in more detail those of conductive structures under the canadian rockies and emslab electromagnetic sounding of the lithosphere and beyond array results for washington and oregon including a conductive strip beneath the cascades volcanoes correlations with high heat flow and seismic parameters make it reasonable to attribute these regional conductors to partial melting and or hot saline water within the craton the north american central plains conductor is discussed this narrow crustal feature is associated with a major fracture zone and age boundary which may be a plate boundary of proterozoic time an array beneath the auroral electrojet for study of the external currents is noted results from four array studies in southern africa are considered two of these relate to the southern cape conductive belt which correlates not with high heat flow but with a large static magnetic anomaly the magnetovariation magnetic and gravity anomalies and geological data can be accounted for if an accumulation of ophiolitic rocks including serpentine is present in the lower crust such an accumulation may have formed at a subduction in proterozoic time two other arrays delineated a conductive belt associated with the southwestern end of the african rift system in namibia subsequent resistivity soundings located a conductor of resistivity 10 ohm m at less than 4 km depth two array studies in india follow one in the north and one in the south the array in the himalayan foothills and indo gangetic plain mapped a conductor transverse to the regional strike this may be a fracture zone produced in the interplate collision with a rise of asthenospheric material such as fluids into the fractures the southern indian array reveals crustal conductors under the indo sri lankan graben and another under the comorin ridge southwest of the tip of the subcontinent array studies in central and southeastern australia and in fennoscandia in regions without large local conductivity anomalies have been used to study conductivity variation with depth a note on the carpathian crustal anomaly is included as an example of combination of response parameters secured at different times to form a virtual array

sedimentary cyclicity in the marine pliocene pleistocene of the wanganui basin new zealand sequence stratigraphic motifs characteristic of the past 2 5 m y earth s climatic history since 2 5 ma has been controlled by milankovitch variations in the planetary orbit comprising alternate periods of glaciation and interglaciation with a dominant frequency of 41 000 yr concomitantly eustatic sea level has fluctuated 70 to 130 m causing rapid transgressions and regressions of the shoreline across the world s continental shelves the resulting sedimentary record is cyclothemic each cyclothem corresponding to a single climate and sea level cycle the wanganui basin new zealand contains a 2 km thick almost complete composite record since isotope stage 100 ca 2 5 ma in the form of 47 superposed cyclothems of shelf origin each cyclothem corresponds to an unconformity bound stratigraphic sequence and typically contains a transgressive systems tract sometimes a mid cycle shell bed a highstand systems tract and sometimes a regressive systems tract no advantage accrues from using transgressive regressive units rather than cyclothems and or sequences in description of the succession six basic sequence motifs represent deposition in locations between the shoreline and offshore shelf i e the hawera birdgrove turakina seafield castlecliff and rangitikei motifs a seventh the nukumaru motif which includes dominant coquina limestone represents deposition in shallow water areas of reduced terrigenous sediment on the flank of the basin the sequence motifs represented in any section change systematically in sympathy with basin scale changes in subsidence and sediment supply in contrast with the 41000 year length of individual glacioeustatic sequences these basin wide tectonic cycles have a periodicity of many hundreds of thousands to a few million years i e that of third or fourth order sequences of the exxon type this coupled with the restriction of strongly cyclothemic sediments to geological periods of known glacio eustasy permiancarboniferous pliocene pleistocene suggests that tectonic subsidence cycles rather than glacio eustasy are the driving forces behind the development of the third and fourth order unconformity bound sequences that are reported to occur throughout the stratigraphic record

forward modelling of the sequence stratigraphic architecture of shelf cyclothems application to late pliocene sequences wanganui basin new zealand we demonstrate a procedure for forward modelling of the sequence stratigraphic architecture i e positions of systems tract boundaries of shelf cyclothems as observed at outcrop sites or in well logs the 1 d model is based on the fact that the deposition of facies within shelf sequences and those defining the key stratigraphic surfaces between systems tracts respond directly to changes in depth between the sea surface and seafloor this accommodation bathymetry model incorporates three reference surfaces sea surface seafloor and lower sequence boundary each of which varies independently as a result of changes in the rates of eustatic sea level sedimentation and subsidence the model input and boundary conditions are an eustatic sea level curve i e late cenozoic deep sea 18o record an independent chronology for the outcrop or well section and a subsidence curve the model outputs are changes in accommodation and palaeobathymetry throughout the sequence and the time missing at erosional sequence boundaries the main variable in the model i e sedimentation rate is established by comparison of a model output bathymetry with the model target palaeobathymetry established from the faunal and facies content of the sequence being modelled when the model output and target are compatible the model sedimentation rate curve is adopted and the theoretical positions of the systems tract boundaries can be read off the model in relation to the lower sequence boundary and compared with independent field based interpretations of their stratigraphic position the model is designed to predict the architecture of sequences as they appear at particular outcrop sites or in well sections its usefulness lies in establishing the timing of accumulation of systems tracts in relation to stages in a eustatic sea level cycle in particular distinguishing between units deposited during highstand versus regressive systems tracts the model is applied to 6th order 41 ka plio pleistocene cyclothems in wanganui basin new zealand where it distinguishes the boundary between highstand systems tracts hst and regressive systems tracts rst the modelling has implications for the definition of systems tracts especially in late cenozoic successions for which the record of eustatic sea level changes is known independently

quaternary marine terrace chronology north canterbury new zealand using amino acid racemization and infrared stimulated luminescence extensive marine terraces along the north canterbury coast of the south island of new zealand record uplift in this tectonically active area although the terraces have been studied previously applications of quaternary geochronological techniques to the region have been limited we use infrared stimulated luminescence irsl amino acid racemization aar and radiocarbon to determine ages of terraces at three locations glenafric motunau beach and haumuri bluff we develop an aar calibration curve for the mollusk species tawera spissa from sites of known age including the sedimentary sequence of the whanganui basin bayesian model averaging of the results is used to estimate ages of marine shells from the north canterbury terraces by using both irsl and aar we are able to confirm ages using two independent dating methods and to identify one irsl result that is likely in error we develop new age estimates for the marine terraces of north canterbury and propose correlations between sites this terrace chronology differs significantly from most previous studies highlighting the importance of numerical dating the most extensive terraces are from marine isotope stages miss 5a and 5c with partial reoccupation of one terrace during mis 3 whereas mis 5e terraces are notably lacking among those dated

electromagnetic induction by the equatorial electrojet summary this paper discusses the effects of currents induced inside the earth at equatorial latitudes due to the currents in the ionosphere and the magnetosphere the horizontal h vertical z and eastward y components of the geomagnetic field at equatorial and low latitude stations around the world are examined for effects due to solar daily sq variations during normal as well as counter electrojet days during solar flares during storm sudden commencements sscs and during the main phase of the magnetic storms the sq z variations show an abnormally large positive peak at indian electrojet stations and to a lesser extent at koror in the forenoon hours when the temporal gradient of sq h is largest at indian longitudes this abnormality is largest during equinoxes and december solstices the nighttime bay disturbance solar flares and ssc produce large impulses in the z field at indian stations and at koror the latitudinal extent of this abnormality is larger for events with shorter periods the disturbance equatorial ring current produces a large decrease of z field around the period in the middle of main phase of the storm when the dst index is rapidly decreasing and not when dst is most negative a strong decrease in the z field is observed at yauca in the american sector during the main phase of the storm the induction effects on the equatorial electrojet seem to be absent in central and eastern parts of south america and in the african region the significant induction effects observed in the recording of the z field at peredinia in sri lanka suggest a wide latitude of abnormal conductivity anomaly distribution in the indo sri lanka longitude sector our present understanding of the conductor being in palk strait between india and sri lanka needs to be revised on the basis of results described in this paper

climate and sea level during oxygen isotope stage 7b on land evidence from new zealand abstract strata at landguard bluff near wanganui new zealand preserve a clear record of relative sea level changes during oxygen isotope stage 7 two relative high sea level stands during stages 7a about 210 000 yr ago and 7c about 240 000 yr ago are separated by a relative low sea level stage 7b that was at least 32 m lower than present pollen analysis of sediment deposited during stage 7b indicates climate at the time was up to 3 c cooler than present the climate and sea level evidence from landguard bluff are consistent with oxygen isotopic evidence from deep sea cores indicating a marked cooling during stage 7 which is closely associated with a summer radiation minimum centered at about 230 000 yr ago in the northern hemisphere

bay sedimentation as controlled by regional crustal behaviour local tectonics and eustatic sea level changes coquimbo formation miocene pliocene bay of tongoy central chile abstract the north facing bay of tongoy in central chile is flanked by topographic highs in the west and east during the miocene and pliocene the bay extended inland at least 30 km farther south than a present it was filled with muds sands coquinas and gravel during a series of transgressions and regressions related to regional and local tectonic movements combined with global sea level variations 87sr 86sr and microfossil dating indicates transgressions between 11 9 11 2 ma 10 1 9 5 ma 9 0 7 3 ma 6 3 5 3 ma 4 3 2 2 ma and 1 7 1 4 ma the regional tectonic behaviour of the crust shows general uplifting from 10 5 ma to 6 9 ma associated with subduction of the juan fernandez ridge jfr beneath this part of the continent subsidence followed between 6 9 and 2 1 ma in the wake of the southeastward migrating jfr the subsequent subduction of an oceanic plateau similar to the jfr caused rapid uplift that led to the final emergence of the bay above sea level the puerto aldea normal fault along the western limit of the study area was reactivated during the regional uplift and subsidence events with reverse faulting occurring during the latter phase sporadic fault reactivation probably triggered the rapid changes in water depth reflected in the recorded vertical succession of facies

dispersed rhyolitic tephra from new zealand in deep sea sediments of the southern ocean dispersed rhyolitic tephra in deep sea piston cores collected from the south pacific sector of the southern ocean have previously been considered to originate from the balleny islands antarctica chemical composition of the materials suggests that a source in new zealand is more likely a strong correlation exists between paleomagnetically determined ages for these deep sea tephra layers and fission track ages determined on volcanic glasses and zircons from tephra sequences in wanganui basin and cape kidnappers new zealand the correlation suggests that the tephra extend more than 5000 km east and south of new zealand

geomagnetic coast and other effects deduced from the new observatory at visakhapatnam india summary coastal effects observed in the long period sq solar quist day ranges and short period changes over 30 min intervals during magnetic substorms bays as recorded at a new magnetic observatory at visakhapatnam on the east coast of india during 1995 in the h z and d elements are analysed and the preliminary results are discussed the results are compared with those from alibag and hyderabad located more or less at the same latitude based on simultaneous 1995 records short period induction vectors are computed and the arrows presented and discussed at the three locations while the enhancement associated with close proximity to the coast in sq z at alibag on the west coast compared to the central inland station of hyderabad enhancement of 17 37 per cent is quite prominent in all three seasons of the year at visakhapatnam it is only marginally observed during the d season at bay frequencies medium sized induction arrows point towards the nearest deep sea conductive body at both alibag and visakhapatnam while it is towards the southeast with a considerably reduced magnitude at hyderabad these induction arrows and the effects on sq z sq h and sq d ranges are discussed in conjunction with the parkinson arrows and sq z sq h and sq d ranges from margao west coast dharwar bellary mahanandi chirala east coast at the latitude of the 16 n profile of an earlier array experiment and the two are interpreted together

sequence stratigraphy of sixth order 41 k y pliocene pleistocene cyclothems wanganui basin new zealand a case for the regressive systems tract this study is based on a late pliocene and early pleistocene approximately 2 6 1 7 ma succession about 1 km thick of 20 sixth order 41 k y duration cyclothems of shelf origin exposed in the rangitikei river valley in the eastern part of wanganui basin the cyclothems correlate with 18 o isotope stages 100 58 and each 41 k y glacialinterglacial stage couplet is represented by an individual depositional sequence comprising transgressive highstand and regressive systems tracts unlike most examples inferred from the stratigraphic record these systems tracts were deposited during phases of known sea level cycles indicated by the contemporary oxygen isotope ice volume curve because of the high rate of subsidence of wanganui basin glacioeustatic sea level falls during most cycles were not of sufficient magnitude to expose the outer shelf thus the rangitikei section provides an exceptional example of regressive strata deposited landward of the contemporary shelf break simple one dimensional modeling shows that moderate to high rates of basin subsidence 1 2 mm yr and low rates of sedimentation 0 2 mm yr during transgressions combined to produce an accommodation surplus at the relative highstand this surplus accommodation was infilled during the late highstand and ensuing fall partly by aggradational highstand systems tract shelf siltstone and chiefly by strongly progradational shoreface sediments of the regressive systems tract rangitikei regressive systems tracts are distinguished from forced regressive systems tracts sensu hunt and tucker 1992 by their different stratal geometry by definition forced regressive systems tracts display an erosional contact with the underlying highstand systems tracts and typically occur as a series of downstepped disjunct shoreline wedges stranded on the shelf and or slope in contrast regressive systems tracts exhibit a gradational lower contact above which parasequences are stacked in a strongly progradational pattern terminated by the superjacent sequence boundary cyclothems display two types of motif termed rangitikei dt depositional transgression and rangitikei nt nondepositional transgression which include the following architectural elements in ascending stratigraphic order 1 a basal sequence boundary that is coincident with either the transgressive surface of erosion which displays small scale up to 50 cm erosional relief and may be penetrated by the ichnofossil ophiomorpha or its deeper water correlative conformity 2 either a thick 5 30 m transgressive systems tract comprising a deepening upward nearshore to inner shelf mixed carbonate siliciclastic lithofacies succession depositional transgression or a thin 2 m transgressive systems tract comprising condensed fossiliferous facies deposited on the sediment starved offshore shelf nondepositional transgression 3 a sharp downlap surface separating condensed fossiliferous facies of the transgressive systems tract from terrigenous siltstone of the superjacent highstand systems tract 4 a highstand systems tract comprising a 10 20 m thick interval of aggradational shelf siltstone and 5 a thick up to 45 m progradational inner shelf to shoreface lithofacies assemblage ascribed to the regressive systems tract condensed shell beds are associated with intrasequence and sequence bounding discontinuities and together with the sedimentological and stratal characteristics of the sequences are important indicators of stratigraphic architecture four types of shell bed are associated with surfaces formed by four different types of stratal termination onlap backlap downlap and flooding surface shell beds cf kidwell 1991 are associated respectively with the transgressive surface of erosion apparent truncation at the top of the transgressive systems tract the downlap surface and local marine flooding surfaces a fifth shell bed type termed a compound shell bed forms in offshore environments where the downlap surface converges with the sequence boundary and elements of both the downlap and the backlap shell beds become mixed or superposed the shell beds mark zones of stratal attenuation and can be used as surrogates for seismic discontinuities when applying sequence stratigraphic concepts at outcrop scale

mid cycle condensed shellbeds from mid pleistocene cyclothems new zealand implications for sequence architecture richly fossiliferous and disconformity bounded facies successions termed mid cycle condensed shellbeds mcs occupy a mid cycle position within depositional sequences in the castlecliff section mid pleistocene wanganui basin new zealand these shell rich intervals 0 1 4 5 m thick comprise the upper of two loci of shell accumulation in castlecliff sequences the lower disconformable contacts are sharp and variably burrowed and are interpreted as submarine transgressive surfaces formed by storm or tidal current erosion at the feather edge of contemporary transgressive systems tracts above i e seaward of this erosion surface macrofossil remains mainly bivalves and gastropods accumulated with little reworking on the inner shelf under conditions of reduced terrigenous sediment supply the upper contacts are sharp transitions from shell rich to relatively shell poor lithofacies parautochthonous shell accumulation was quenched by downlapping highstand systems tract shelf siltstones and muddy fine sandstones castlecliff mcs together with the basal shell rich part of overlying highstand systems tracts occupy a stratigraphic position which corresponds to the condensed section that forms at the transgressive highstand systems tract boundary in the sequence model of haq et al 1987 palaeoenvironmental analysis indicates that castlecliff mcs are substantially if not entirely transgressive deposits this study therefore shows that the condensation maximum within a depositional sequence does not necessarily bracket the transgressive systems tract highstand systems tract boundary

magnetostratigraphic lithostratigraphic and tephrostratigraphic constraints on lower and middle pleistocene sea level changes wanganui basin new zealand wanganui basin north island new zealand contains a complex sedimentary record of lower and middle pleistocene sea level changes palaeomagnetic results allow identification of the matuyama brunhes transition the jaramillo subchron and the cobb mountain subchron correlations of rhyolitic tuff horizons across the basin are consistent with magnetostratigraphic correlations between sections isothermal plateau fission track itpft ages of 1 05 0 05 ma and 1 63 0 15 ma on two tuffs potaka pumice and pakihikura pumice respectively are consistent with the interpreted magnetostratigraphy and also with the astronomically tuned timescale of odp site 677 magnetostratigraphy and itpft ages allow correlation of sedimentary cycles at wanganui with odd numbered oxygen isotope stages 17 31 in deep sea cores the stratotype section for the new zealand castlecliffian stage is shown to be incomplete relative to other studied sections in the basin below stage 31 the character of the cyclothems changes at wanganui from marine dominated to a greater representation of non marine and estuarine strata this change may be partly related to a change in amplitude and frequency of climatic cycles identified in oxygen isotope records but the primary cause is likely to be increased basinal uplift

cyclostratigraphy of middle pliocene mid shelf to upper slope strata eastern wanganui basin new zealand correlations to the deep sea isotope record abstract rangitikei valley in eastern wanganui basin contains a well exposed 750 m thick middle pliocene succession that accumulated during the gauss chron traditional facies analysis involving laboratory grain size determinations and benthic foraminiferal census on a suite of closely spaced 5 m samples show that the utiku group lower 350 m accumulated predominantly in a mid shelf environment the overlying mangaweka mudstone 400 m thick accumulated in an outer shelf to upper slope environment combined with the identification of sequence stratigraphic surfaces sequence boundary transgressive surface of erosion and downlap surface four sequences have been identified in the utiku group in the outwardly massive mangaweka mudstone there is no outcrop evidence for sequences seven sedimentary cycles are nevertheless defined by changes in grain size and by variations in foraminiferal paleobathymetry the utiku group sequences show mostly asymmetric sequence architecture with comparatively thin tsts rapid deepening across the utiku group mangaweka mudstone boundary at 3 0 ma involving an increase in water depth of at least 100 m that persisted until 2 55 ma orignated tectonically probably as a result of plate boundary interactions this is the second of two known rapid deepening tectono sedimentary events each separated by about 1 5 my higher order sea level cyclicity involving 11 sedimentary cycles as presently defined are superimposed upon this second tectono sedimentary cycle independent magnetostratigraphies allow the sedimentary cycles to be correlated to the astronomically tuned oxygen isotope stratigraphy for odp site 846 for the interval 3 55 3 0 ma the sedimentary cyclicity reflects the periodicities of the more major enriched 18 o peaks which range from 41 ka mg2 to m2 to 210 ka mg6 to mg2 thus the duration of cyclicty in the utiku group closely corresponds to the duration between significant sea level lowering events which are marked by glacial 18 o shifts of 0 4 on the odp site 846 benthic 18 o curve

milankovitch 41000 year cycles in lithofacies and molluscan content in the tropical middle miocene nyalindung formation jawa indonesia abstract nine cyclothems based on changes in sedimentary facies and molluscan fossil associations are identified in the middle miocene 12 ma lower part of nyalindung formation cijarian river section sukabumi west jawa province indonesia molluscan associations were studied in 75 blocks collected through the succession 47 species of autochthonous molluscs belonging to 38 genera were separated from the blocks five molluscan associations were recognized through comparison of these species with their closest living analogues a sedimentary cycle consists of two conformable lithologic units in ascending order a gravelly shellbed or gravelly conglomeratic sandstone and a muddy fine to medium grained sandstone the exception is the basal cycle which has an intercalation of limestone the systematic change in the molluscan fossil associations within individual cycles indicates that lithological changes correspond to changes in water depth with an amplitude of about 30 m the short time period represented by the section and the thin units many not more than 2 m thick indicates that the main cause of the cyclicity was orbitally induced climate change representing milankovitch scale cycles of 41 000 years this appears to be the first time milankovitch sea level cycles have been reported from the tropical regions of the earth

palaeomagnetic location of the jaramillo subchron and the matuyama brunhes transition in the castlecliffian stratotype section wanganui basin new zealand abstract magnetostratigraphy is described for the lower part of the castlecliff section in wanganui basin new zealand based on analysis of multiple samples from 37 horizons the castlecliff section is the stratotype of the middle pleistocene castlecliffian stage and comprises eleven unconformity bound sequences which accumulated at inner shelf depths during interglacials a range of rock magnetic experiments undertaken on representative lithologies within the section show that the bulk of the remanence in all specimens is carried by ferrimagnetic mineral close to magnetite in composition in the stable single domain or pseudo single domain size range however at some sites post depositional chemical changes appear to have produced small amounts of another ferrimagnetic mineral chiefly within the superparamagnetic single domain size range resulting in hard secondary components of magnetization nevertheless at most sites the primary component of remanence was clearly identified by stepwise demagnetization four magnetozones are identified and these can be correlated to the magnetic polarity time scale using existing biostratigraphic constraints the section sampled spans the interval from below the jaramillo subchron to above the matuyama brunhes boundary the matuyama brunhes transition extends over 10 5 m of section within the upper westmere siltstone virtual geomagnetic pole positions describe an equatorial excursion in an otherwise far sided transition path these represent the first published data on the occurrence of the matuyama brunhes boundary on land in new zealand

climate of the last glaciation in new zealand based on aerosolic quartz influx in an andesitic terrain abstract on western north island new zealand a record of climatic change during the last glaciation is preserved in a terrestrial coverbed sequence of dominantly andesitic provenance here a succession of five loess like andisol units postdates the global high sea level stand of oxygen isotope substage 5e

a three dimensional numerical model study of electromagnetic induction around the indian peninsula and sri lanka island abstract magnetic field variations recorded using an array of magnetometers have shown earlier significant anomalies at some southern stations of india e g annamalainagar adiramapatnam and trivandrum the nature of anomalous horizontal and vertical fields and their persistence to periods of the order of hours cannot be explained in terms of the usual coast effect alone some authors have suggested that these anomalies could be caused by the electric currents induced in the deep ocean but channelled through a good conductor situated below the palk strait and gulf of manowar between india and sri lanka to investigate the effect of such a deep conductor possibly in the lower crust or upper mantle a three dimensional model of india sri lanka and the surrounding coast lines has been studied using a numerical technique with the aid of the well known finite difference numerical method for partial differential equations solutions of the magnetic fields have been computed for two different models 1 without conductor and 2 with a conductor in the palk strait gulf of manowar region below the ocean floor the results are presented in the form of contour plots and spatial behaviour of the amplitudes of three magnetic field components h d z at the surface of the earth contour plots clearly reveal that when a highly conducting sub surface structure is introduced in the palk strait region the currents tend to flow along the direction of the conductor and contribute to enhancement of the magnetic field amplitudes along the east coast of the indian peninsula and west coast of sri lanka island the amplitude plots show that in general the numerical results for the model with the sub surface conductor tend to agree with the results of the magnetometer observations thereby supporting the hypothesis of a sub surface conducting structure between india and sri lanka

the conductosphere depth at equatorial latitudes as determined from geomagnetic daily variations the structure of the conductosphere at equatorial latitudes is investigated by analyzing geomagnetic daily variations gdv data to do so the magnetic field induced in a multilayered model by an external source of finite size that reproduces the external part of these variations is computed latitudinal profiles of the total field produced at ground by the assumed external source are then found and compared with the measured gdv data results are applied to equatorial zones in peru africa and india

late quaternary transgressive regressive sequences from taranaki continental shelf western new zealand abstract interpretation of seismic reflection profiles 3 5 khz airgun and piston core and borehole stratigraphic logs collected from mid outer shelf depths 50 130 m on the taranaki continental shelf western new zealand have delineated at least 4 alternating late quaternary seismic and lithologic couplets each couplet comprises an acoustically transparent upper silty unit that overlies a highly reflective sandy unit characterised by a channelised erosive base radiocarbon and biostratigraphic nannofloral dating of selected samples provides chronostratigraphic control for the succession indicating that the entire sequence is probably late quaternary in age based mainly on nannofossil paleoenvironmental interpretations and seismic reflection characteristics it is proposed that the silty units represent interglacial highstand deposits and that the intervening sandy units were deposited either as glacial lowstand or transgressive nearshore deposits that developed under rising sea level conditions erosive irregular basal unconformities were probably developed during relative sea level fall and represent type 1 sequence boundaries there may also have been a component of wave planation during the subsequent transgression high amplitude channel fill seismic units are possibly fluvial and or paralic sediments deposited during the sea level lowstand and or the ensuing transgression tentative correlation of late quaternary units on the taranaki shelf is made to the deep sea oxygen isotope stage curve to provide temporal resolution of the stratigraphic section four possible sedimentation models are considered based on different temporal interpretations of the observed litho and seismic stratigraphy estimated sedimentation rates for each model are compared to existing data sets as a validation tool the data are inconclusive but appear to support scenario 1 which is characterised by moderate average sedimentation rates over the past 300 000 years typically 0 57 m kyr with an anomalous phase of slow deposition or non deposition and or erosion during stage 6

recurring global sea level changes recorded in shelf deposits near the g m polarity transition wanganui basin new zealand implications for redefining the pliocene pleistocene boundary abstract a well exposed 1 km thick association of late pliocene and early pleistocene ca 2 6 1 7 ma strata in wanganui basin new zealand contains a progradational stack of twenty 5th order 41 ka duration depositional sequences that accumulated in shelf to shoreface paleoenvironments in response to global glacioeustatic sea level fluctuations the sequences are correlated with 18o isotope stages 100 58 and each 41 ka glacial interglacial stage couplet is represented by an individual sequence comprising transgressive tst highstand hst and regressive rst systems tracts that can be readily related to generic sequence stratigraphic models in general deposition of each of the sequences occurred during odd numbered interglacial isotope stages and the sequence boundaries developed during the maxima of even numbered glacial isotope stages the key palaeomagnetic tiepoints used for pinning the isotope record to the section are the gauss matuyama boundary 2 60 ma in stage 104 and the top of olduvai subchron 1 77 ma in stage 63 a deeply incised sequence boundary with up to 30 m of relief at the base of te rimu sand represents the first widespread subaerial exposure in wanganui basin during the matuyama chron it is correlated with the high amplitude positive glacial 18o shift in isotope stage 100 which is considered to mark the initiation of major northern hemisphere continental glaciations at ca 2 52 ma the overlying hautawa shellbed containing the subantarctic bivalve chlamys delicatula defines the base of the nukumaruan stage and represents the earliest faunal evidence of climatic cooling in new zealand pliocene pleistocene marine sequences the sequence boundary at the base of hautawa shellbed is correlated with isotope stage 98 ca 2 48 ma traditionally the pliocene pleistocene boundary in new zealand was located at the base of hautawa shellbed but beu and edwards 1984 showed that the boundary as defined in the vrica stratotype astronomically calibrated age ca 1 81 ma actually lies in the upper part of the nukumaruan stage the hautawa shellbed which lies closer to the gauss matuyama palaeomagnetic transition 2 60 ma is therefore much older than the currently defined pliocene pleistocene boundary from a new zealand perspective a more logical position for the pliocene pleistocene boundary would be close to or just above the gauss matuyama polarity transition such a position would take advantage of the boundaries proximity to a readily identifiable polarity reversal and lie close to the time of initiation and development of major northern hemisphere ice sheets

resonance and morphological stability of tidal basins the paper describes the concept of a network model for the morphological behaviour of a near resonant multiple inlet tidal basin as part of a model system which includes the barrier island coasts and the outer deltas it addresses the question whether a small interference somewhere in such a basin can have major effects on sediment transport and morphology elsewhere in the system in order to explain the basic ideas of the model only the main tidal constituent m2 and the associated topography induced residual current are considered not the overtides furthermore the model concerns only non cohesive sediment sand in spite of these simplifications the model concept is shown to be effective in that it results in a morphological evolution equation for each branch of the network and a picture of the influence of each branch on the resonance sensitivity of the system as a whole

lower pleistocene to present structural deformation and sequence stratigraphy of the continental shelf offshore eel river basin northern california seismic stratigraphic sequences and deformational features are mapped beneath the continental shelf of the offshore eel river basin of northern california using a closely spaced high resolution multichannel seismic grid geometries of sequences and morphologies of bounding unconformities reflect competing tectonic and glacioeustatic influences producing shifting sedimentation patterns in the offshore basin during the last v1 myr estimated timing of unconformity formation correlates generally with a deep ocean global n 18 o curve both before and after a v500kyr transition from 41 kyr to 100 kyr dominated cycles we suggest that glacioeustatic fluctuations are the dominant control on unconformity formation basinwide however regional tectonic influences on sequence development are also observed folding associated with gorda north america plate convergence ended progressively from south to north between v1 0 ma and v500 ka in response to northward migration of the mendocino triple junction mtj since v500 ka continued encroachment of the mtj produces rotation of preexisting structures uplift of the table bluff anticline tba related periods of channel incision south of the tba and generally reduced sediment preservation across the shelf mtj related uplift may also have induced formation of eel canyon over the past v1 0 myr a dominant northern sediment source becomes progressively less important a southern source probably the paleo eel river has become dominant since v750 ka seismic unconformities fall into two categories 1 irregular surfaces of limited mappable extent interpreted as incision exposure surfaces forming during relative sea level lowstands and 2 smooth laterally extensive regional unconformities interpreted as ravinement surfaces that erode lowstand surfaces in all but deeply incised areas during sea level transgressions a sequence stratigraphic model for sediment deposition and preservation on the eel river shelf predicts that preserved sediment on the eel margin is dominated by fluvially derived highstand silts and muds deposited by longshore directed currents and waves lowstand sediments are preserved only in fluvial channels infilled during late lowstand early transgression preserved transgressive sediments are likely limited to a thin veneer of well sorted coarse sediment or shell debris deposited above the transgressive ravinement future deep coring will be required to confirm these predictions 2002 elsevier science b v all rights reserved

500 000 year paleomagnetic record from new zealand loess abstract a paleomagnetic record of secular variation has been obtained from a 17 4 m long core drilled from loess in north island new zealand three dated rhyolitic tephra occur in the loess core at depths of 1 5 3 4 and 13 0 m with ages of 22 500 42 000 and 370 000 years respectively the base of the core is estimated to be 500 000 years old which makes this the longest continuous loess sequence yet described from the southern hemisphere two periods of anomalously low inclination in the core are correlated with the mungo event ca 35 000 years ago and the emperor event ca 490 000 years ago the blake event ca 115 000 years ago is not recorded

isothermal plateau fission track ages of tephra beds in an early middle pleistocene marine and terrestrial sequence cape kidnappers new zealand abstract at least nine rhyolitic eruptive events or sequences are interbedded with alternating marine and terrestrial sediments of early middle pleistocene age at cape kidnappers new zealand the sediments represent one of the few high resolution glacio eustatic sea level records in new zealand we have obtained ages of 0 99 0 09 1 00 0 10 0 86 0 05 and 0 79 0 06 ma in ascending stratigraphic order for four prominent tephra beds from isothermal plateau fission track dating of their glass shards these ages are older than previous fission track determinations but are in agreement with tephra correlations to other sections ar ar data and magnetostratigraphy however the upper part of the sequence previously interpreted as the brunhes chron may have been affected by normal overprinting and is instead older the tephra record suggests a higher frequency of eruptions than is indicated by the proximal ignimbrite record in the taupo volcanic zone the new tephra ages indicate that the section was deposited in the interval 1 0 0 65 ma at a rapid average sedimentation rate of ca 1 m ka

transgressive systems tracts and onlap shellbeds from mid pleistocene sequences wanganui basin new zealand abstract sequences in the castlecliff section mid pleistocene wanganui basin new zealand are composed of transgressive and highstand systems tracts and were deposited in response to fifth order c 100 ky and sixth order c 40 ky glacio eustatic fluctuation on the paleo taranaki shelf castlecliff transgressive systems tracts tst the topic of this paper are ideally represented by fining upward facies successions up to 22 m thick above a basal sequence bounding ravinement surface these successions usually comprise a subtidal cross bedded shell rich gravel onlap shellbed which is overlain by a fining upward succession of inner shelf siltstones and silty fine sandstones tst successions are capped by mid cycle condensed shellbeds discussed in detail elsewhere which represent terrigenous sediment starvation at the seaward feather edge of tst deposition castlecliff tst facies architecture differs substantially from other examples of transgressive stratigraphy first castlecliff tst are relatively thick in comparison to overall cycle thickness second sequence bounding ravinement surfaces at the base of castlecliff tst everywhere rest directly on shelf siltstone constituting the truncated highstand systems tract of the underlying sequence this indicates erosion of 1 coeval paralic tst landward of the ravinement surface 2 the lowstand coastal plain comprising the sequence boundary sensu stricto as well as any incised fluvial channels and 3 the presumably coarsening upward upper part of the underlying sequence such differences can be reconciled by consideration of local factors relating to the active tectonic setting of wanganui basin deposition occurred in a storm influenced shelf embayment adjacent to a rising hinterland in this setting high energy transgressive shorefaces scoured 10 20 m at the same time the embayed coastline provided a trap for the abundant sediment supply

regional electromagnetic induction around the indian peninsula and sri lanka a three dimensional numerical model study using the thin sheet approximation abstract further to other recent numerical studies of geomagnetic induction in southern india the thin sheet algorithm developed at the university of victoria has been used to investigate the three dimensional problem of induction by a uniform source over the indian peninsula and sri lanka with this algorithm it is not necessary to assume that the region is surrounded by a normal structure but the limitations imposed by grid size and the given conductivities for the crust and mantle have restricted our study to an inducing field of 20 min period solutions have been computed for two different models 1 with only the conductivity contrast arising from land and seawater of variable depth present and 2 with additional sub surface conductors included in the palk strait gulf of manowar region underneath or near the comorin ridge and along the west coast fault results are presented for uniform magnetic sources oriented in both the northward and westward directions to distinguish the effect of different polarizations the correspondence between the observed and computed parkinson arrows at the southern array stations suggests the existence of the three sub surface conductors

stability analysis of a two inlet bay system abstract the stability analysis for a double inlet bay system is applied to an inlet system resembling big marco pass and capri pass on the lower west coast of florida since the opening of capri pass in 1967 the length of big marco pass has increased from 2000 m in 1967 to 3000 m in 1988 and the cross sectional area has decreased from 1200 m 2 in 1967 to 1000 m 2 in 1988 since 1967 the cross sectional area of capri pass has steadily increased and in 1988 was 700 m 2 tides off the inlets are of the mixed type with a diurnal range of 1 m the gross littoral transport rate in the vicinity of the inlets is estimated at 150 000 m 3 yr 1 for each inlet the maximum tidal velocities are calculated as a function of the gorge cross sectional areas using a lumped parameter model to describe the hydrodynamics of the flow in the model it is assumed that the bay level fluctuates uniformly and the bay surface area remains constant the velocities are used to calculate the tidal maximum of the bottom shear stress in each inlet as a function of the cross sectional areas of the two inlets closure surface values of the equilibrium shear stress are derived from an empirical relationship between cross sectional area and tidal prism for stable inlets along the west coast of florida closure surfaces and equilibrium stress values are calculated for values of friction factors ranging from f 4 10 3 to f 6 10 3 using the closure surfaces and equilibrium stress values the equilibrium flow curve for each inlet is determined the equilibrium flow curve represents the locus of the combination of cross sectional areas for which the actual bottom shear stress in the inlet equals the equilibrium shear stress based on the equilibrium flow curves and the known values of the cross sectional areas of the two inlets in 1988 it is expected that ultimately big marco pass will close and capri pass will remain as the sole inlet with a cross sectional area of 1250 m 2 and a maximum tidal velocity pertaining to a diurnal tide of 0 85 m s 1

distributed deformation due to coupling across a subduction thrust mechanism of young tectonic rotation within the south wanganui basin new zealand paleomagnetic data from pliocene sedimentary strata in the south wanganui basin new zealand document clockwise tectonic rotation west of and increasing toward the main zone of deformation axial tectonic belt associated with the australia pacific plate boundary zone in the north island of new zealand measured rotation with respect to the australian plate increases from 1 4 3 9 80 km west of the axial tectonic belt to 6 5 2 0 and 13 2 3 1 at 45 km and 20 km west of the axial tectonic belt respectively these measurements indicate that 1 deformation associated with plate convergence occurs across a wide region up to 270 km west of the hikurangi trench and 2 in the past 2 5 m y at least 30 km of transcurrent motion and 10 km of shortening at the plate boundary have been accommodated within the south wanganui basin by distributed shear west of the plate boundary zone proper the data support a model suggesting that the wanganui basin is a lithospheric flexure basin driven by high friction at the plate interface this strain in the south wanganui basin and inferred high friction across the plate interface at the basin9s eastern margin have occurred since 2 5 ma

sequence concepts at seismic and outcrop scale the distinction between physical and conceptual stratigraphic surfaces abstract the sequence stratigraphic terms maximum flooding surface and downlap surface as currently applied are ambiguous examples of these intra sequence surfaces are summarised from high frequency mid pleistocene sequences and from a cretaceous recent seismic megasequence both from new zealand at any one locality a mid pleistocene sequence contains up to four stratal discontinuities in ascending order the sequence boundary ravinement surface local flooding surface and downlap surface these physical surfaces which occur in outcrop are regionally diachronous and should be differentiated from theoretical isochronous horizons such as the time of maximum flooding horizon corresponding to maximum shoreline transgression and the time of peak eustatic or local relative sea level horizons corresponding to the highpoint of the eustatic and relative sea level cycles respectively in seismic studies the boundary between the transgressive and highstand systems tracts is usually located at the downlap surface on the basis of a major thermo tectonic sea level cycle in the canterbury basin it is shown that the downlap surface is not a single regional surface and that the change in slope associated with toes of successive prograding clinoforms rises in stratigraphic height basinwards the downlap surface therefore does not usually coincide with the maximum flooding horizon in plio pleistocene cyclothems a discrete unit the mid cycle shellbed straddles the contact between the transgressive and highstand systems tracts this unit might be classified within its own systems tract the condensed section systems tract csst alternatively the position of the boundary between the transgressive and highstand systems tracts can remain unspecified or unknowable

revision of the marine chronology in the wanganui basin new zealand based on the isothermal plateau fission track dating of tephra horizons abstract the occurrence of tephra horizons in basins adjacent to volcanic arcs provide an excellent opportunity for establishing a reliable chronostratigraphic framework for detailed sedimentological studies in this study three widespread and stratigraphically important rhyolitic tephra horizons interbedded in plio pleistocene strata of the wanganui basin new zealand are dated by application of the isothermal plateau fission track itpft technique to hydrated glass shards all glass samples were corrected for annealing and consequently yield reliable ages rangitawa tephra yielded statistically indistinguishable ages from three localities that are in excellent agreement with recently determined zircon fission track age estimates of ca 0 35 ma itpft ages of 1 05 0 05 and 1 63 0 15 ma for potaka pumice and pakihikura pumice respectively are considerably older than previous ft estimates but consistent with new magnetostratigraphic data that places the potaka within the jaramillo subchron and pakihikura within the matuyama chron between the cobb mountain and olduvai subchrons combining our fission track ages with the magnetostratigraphy the true age of sediments within the wanganui basin is found to be significantly underestimated sedimentation rates of between ca 680 630 m ma from 1 63 ma to 0 35 ma are calculated in the eastern part of the basin and are much lower than those calculated using the previous ft chronology this new itpft age data demonstrates that the existing plio pleistocene marine chronology in new zealand will require age revision and has important implications when considering the evolution of several other sedimentary basins in southern north island that contain the same itpft dated tephra horizons

a numerical model of beach morphological evolution due to waves and currents in the vicinity of coastal structures a numerical model was developed of beach morphological evolution in the vicinity of coastal structures the model includes five sub models for random wave transformation surface roller development nearshore wave induced currents sediment transport and morphological evolution the model was validated using high quality data sets obtained during experiments with a t head groin and a detached breakwater in the basin of the large scale sediment transport facility at the coastal and hydraulics laboratory in vicksburg miss usa the simulations showed that the model reproduced well the wave conditions wave induced currents and beach morphological evolution in the vicinity of coastal structures both salient and tombolo formation behind a t head groin and a detached breakwater were simulated with good agreement compared to the measurements c 2011 elsevier b v all rights reserved

proposed relation between anomalous geomagnetic variations and the tectonic history of south india abstract anomalous geomagnetic variations have been observed at all geomagnetic stations in south india and they have earlier been attributed to ocean and crustal conductors the spectral character of induced variations indicate that in addition to coastal effects and channelling of currents through the palk straits there is a concentration of currents in a conducting body at deeper levels in the crust or mantle current thinking on crustal evolution and the influence of precambrian lineaments on tectonism and mineralisation up to recent times provides support for the conjecture that zones of high electrical conductivity exist in the crust which are related to tectonic and mineral influences the eastern ghats and granulite terrain of south india and sri lanka are probably associated with such a zone of fundamental weakness in the crust extended graphite mineralisation along the eastern ghats occurrence of economic graphite deposits near trivandrum and in sri lanka and the association of alkaline and ultrabasic metallic minerals with deep faults in south india are indications of the possible chemical causes of high electrical conductivity in some regions of the crust similar relations between induced anomalous variations and tectonism and mineralisation in the precambrian crystalline crust have been found in north america and scotland however the regions of high electrical conductivity have not yet been mapped in detail in south india to confirm such a relationship