the architectural variability of small scale cycles in shelf and ramp clastic systems the controlling factors many sedimentary successions are composed of metre to decametre scale cycles exhibiting various stratal architectures that depend on the complex interplay among several syndepositional controlling factors these controlling factors may produce extremely different stratal and facies architectures along relatively brief distances in the same basin but in contrast they also may form similar architectures in basins that experience a radically different tectonic setting the recognition of factors that controlled the architecture of small scale cycles therefore is very important to reconstruct the depositional history of sedimentary successions these factors include 1 the interplay between the rate of accommodation development and the rate of sediment supply a s 2 the amplitude and shape of the relative sea level curve 3 the position in the shoreface shelf system 4 the basin physiography 5 the shoreline trajectory 6 the climate driven environmental energy 7 the siliciclastic input vs carbonate production shoreface to shelf small scale cycles can be grouped into three main categories r cycles showing a dominant regressive interval t r cycles with transgressive and regressive intervals of similar thickness t cycles showing a dominant transgressive interval although some depositional settings may favour the deposition of a particular type of cycle these cycle motifs appear to be mainly controlled by the interaction of local and wider scale controlling factors for example t cycles may be present in both subsiding and uplifting settings depending on the interplay between the a s and the other factors cited above as a result r t r and t cycles may be recognized within the same depositional system these evidences suggest that care must be taken to apply general models that predict the stratal architecture of cycles mainly in function of the long term a s the correct prediction of the cycle architecture is important also for hydrocarbon researches as the thickness of potential reservoir deposits is the result of the interplay among factors discussed here

stratigraphic variability due to uncertainty in model boundary conditions a case study of the new jersey shelf over the last 40 000 years abstract prediction of stratigraphy by numerical sedimentary models is influenced by a series of geological boundary conditions paleo bathymetry sediment supply sea level ocean storm climate and tectonics these boundary conditions evolve non linearly over time and have considerable uncertainty this study explores the impact of the uncertainty of complex boundary conditions on stratigraphic prediction two numerical models are sequentially run the climate driven hydrological model hydrotrend generates a time series of discharge and sediment load at the river mouth which then feed into the process based stratigraphic model sedflux 2d sedflux disperses sediment in the fluvio marine domain the bedload fluxes drive floodplain and mouthbar deposition while suspended sediment is dispersed in the ocean through hypopycnal plumes seafloor sediment is reworked by ocean storms failures and subsequent transport as sediment gravity flows sedflux records the thickness of the deposited sediment and the grain size preserved over time along a longitudinal profile one base case simulation and 20 sensitivity tests of the new jersey shallow margin over the last 40 000 yr serve to explore the impact of uncertain boundary conditions initially the shelf is exposed and arctic conditions prevail in the drainage area paleo temperature and precipitation estimates differ significantly between different community climate system model realizations impacting river sediment flux predictions subsequently high sediment supply from the rivers draining the melting laurentide ice sheet has a dominant impact on the shelf stratigraphy drainage basin characteristics are strongly controlled by the hard to define details of the laurentide ice sheet dynamics over the last 10 000 yr the shelf becomes sediment starved and storm dominated but the paleo storm conditions are uncertain and thus require a wide range of values shallow seismic data have been used to validate the large scale deposited thicknesses of the sedflux prediction the base case sedflux prediction for the sedimentary architecture of the new jersey shelf is consistent with the acoustically observed distribution of major sediment wedges due to the strong forcing of the relatively well constrained sea level changes the range in thickness predictions over the sensitivity tests is well within the lateral variations reconstructed from the observed seismic data sedflux predictions and a data set of 654 seafloor samples taken on the new jersey shelf between 50 and 150 m water depth shows a subtle fining towards deeper water sedflux systematically overpredicts the component of fine sediments at the seafloor likely because the model does not predict shell hash paleo storm climate is found to have a high uncertainty and strongly impacts the predicted grain size distributions we advocate a modeling approach which couples a series of sensitivity experiments to a predicted base case experiment in that way the stratigraphic variability caused by uncertainty in the boundary conditions is evident for later users

intensified deep pacific inflow and ventilation in pleistocene glacial times the production of cold deep waters in the southern ocean is an important factor in the earth s heat budget1 the supply of deep water to the pacific ocean is presently dominated by a single source the deep western boundary current east of new zealand here we use sediment records deposited under the influence of this deep western boundary current to reconstruct deep water properties and speed changes during the pleistocene epoch in physical and isotope proxies we find evidence for intensified deep pacific ocean inflow and ventilation during the glacial periods of the past 1 2 million years the changes in throughflow may be directly related to an increased production of antarctic bottom water during glacial times possible causes for such an increased bottom water production include increasing wind strengths in the southern ocean or an increase in annual sea ice formation leaving dense water after brine rejection and thereby enhancing deep convection we infer also that the global thermohaline circulation was perturbed significantly during the mid pleistocene climate transition between 0 86 and 0 45 million years ago

origin of the torlesse terrane and coeval rocks south island new zealand the carboniferous to lower cretaceous torlesse terrane and haast schist derivatives constitute the major part of the complexly deformed facies of the eastern province of new zealand strata consist mainly of quartzofeldspathic graywacke and mudstone intercalated with minor but widely distributed conglomerate and volcanics with associated chert and limestone clastic rocks were deposited largely by sediment gravity flow mechanisms in a deep marine environment also present are a few highly fossiliferous shallow marine and terrestrial deposits of limited areal extent which rest unconformably on or in fault contact with torlesse flysch several periods of deformation are recognized and melange is present on both local and regional scales metamorphism ranges from zeolite to greenschist facies the bulk of the rocks fall into five areally extensive and mutually exclusive fossil zones of the following ages permian atomodesma middle triassic early late triassic torlessia late triassic monotis and late jurassic early cretaceous contacts between major fossil zones are mainly tectonic petrographic analysis permits subdivision of torlesse sandstones into five major petrofacies that correspond in age to the five major fossil zones the sandstone petrofacies mainly arkosic together with the composition of conglomerate clasts mainly indurated torlesse rocks indicate that the source terrane was a continental volcano plutonic arc probably part of gondwanaland coupled with autocannibalistic reworking of older uplifted torlesse rocks in contrast to the quartzofeldspathic nature of the torlesse coeval sedimentary rocks of the eastern province are volcanogenic they are thought to represent related forearc basin maitai murihiku terranes and trench complex caples terrane deposits derived from a volcanic island arc brook street terrane three petrofacies are established for maitai murihiku and caples sandstones the petrofacies indicate a common evolving immature to submature volcanic island arc source for these terranes a reconstruction of new zealand s eastern and western provinces is proposed in permian and triassic times the torlesse was deposited in trench slope or borderland basins along a trench transform margin fronting a continental volcano plutonic arc source western province gondwanaland deposition was spasmodic but voluminous and was accompanied by concurrent deformation and accretion resulting in parallel belts of torlesse rock younging outward from the gondwanaland margin at the same time the brook street terrane volcanic arc and associated terranes were forming to the west of the torlesse site separated from gondwanaland by a marginal sea in latest triassic or early jurassic times the torlesse was rafted into the volcanic arc system via transform faulting approximately parallel to the gondwana margin the collision event resulted in tectonic thickening of torlesse and caples rocks at the plate interface and metamorphism to haast schist the source was then dominated by older partly metamorphosed torlesse terrane newly uplifted along the collision front closing of the marginal sea behind the brook street terrane in late jurassic early cretaceous times resulted in juxtapositioning with the western province gondwanaland along the median tectonic line

parasequence types in shelfal mudstone strata quantitative observations of lithofacies and stacking patterns and conceptual link to modern depositional regimes mudstone strata have a vast variety of physical biogenic and chemical attributes at the lamina to bed scale approximately millimeters to decimeters thick our observations of more than 7 km of paleozoic to cenozoic mudstones revealed ordered patterns in this variety i e recurrent associations of lithofacies bedding style sedimentary structures and stratal architecture at bedset to parasequence scales approximately decimeters to meters thick we quantified characteristics of each association and their stacking patterns in vertical succession and linked them to sets of depositional processes most shelf mudstone strata appear to have accumulated in one of three facies association successions fass that can be related to depositional regimes through characteristic modes of sediment transport and accumulation as well as variations in benthic energy and oxygen levels we interpret these three fass as records of mud accumulation on different portions of continental shelves that were dominated by storm waves river floods or tidal currents each fas records a distinct parasequence type this approach can help fully integrate insights from oceanographic studies into more robust interpretations of the rock record and rock property maps

middle upper pleistocene record of 100 ka depositional cycles on the southern tuscany continental margin tyrrhenian sea italy abstract five unconformity bounded depositional sequences have been seismically defined on the tyrrhenian margin offshore southern tuscany italy the set of sequences encompasses a 500 ka interval each sequence recording a 100 ka orbitally driven climate eustatic cycle similarly to most of quaternary continental margins sequences on the southern tuscany margin show an overall regressive motif reflecting shelf sediment progradation basically during the prolonged phases of sea level fall that characterise the middle upper pleistocene 100 ka cyclicity on seismic profiles however progradational units within each sequence display a variable clinoform geometry interpreted as a record of the alternation of highstand falling and lowstand intervals within 100 ka cycles the observed geometric variability is thus used as a key for separating systems tracts otherwise merging into a general progradational regressive sedimentary body composing the bulk of each sequence on a longer term the interplay between sea level changes modulated by 100 ka cycles and regional subsidence controls the stratigraphic architecture and the growth pattern of the continental margin this effect is documented by the overall aggradational retrogradational stacking pattern of sequences superimposed on shelf margin progradation and reflecting the renewal of accommodation space landward of the shelf margin and its exploitation at each cycle

late quaternary marine isotope stages 6 1 seismic sequence stratigraphic evolution of the otago continental shelf new zealand abstract a proposed chronostratigraphic model for the late quaternary evolution of the otago continental shelf new zealand includes fluvially incised sequence boundaries eroded during marine isotope stages 2 4 and 6 bounding three sequences subdivided into lowstand transgressive and highstand regressive systems tracts datable material is limited to the uppermost 1 m of the sequence and consequently the model is based on correlation of new high resolution seismic reflection data geopulse to a compilation of independent global sea level curves a second chronostratigraphic model that lacks a stage 4 sequence boundary and distinct stage 3 highstand forced regressive deposit is discounted because its subsidence corrected paleoshoreline depths do not match lowstands in the eustatic curves or temporally constrained sequences at other far field locations in the preferred chronostratigraphic model sea level lowstands during stages 2 4 and 6 reached maximum depths of 126 131 m 101 111 m and 116 135 m respectively producing sequence boundaries landward pinching deltaic wedges on the outer otago shelf and submarine canyon incision lowstand paleoshoreline depths have been corrected for subsidence from thermal cooling sediment compaction and loading but may be erroneously deep owing to erosion of paleoshoreline indicators clastic shallow marine wedges and back barrier valley fill deposits accumulated during the stage 6 5 4 3 and 2 1 marine transgressions contrary to the traditional sequence stratigraphic model deltaic and strandline units deposited during highstand through falling sea level stages 5 4 3 2 1 volumetrically dominate otago late quaternary sequences discrete units and minor marine erosion surfaces within the transgressive and regressive systems tract deposits are interpreted as strong evidence for seventh 20 ka or higher order sea level fluctuations influencing sedimentation on the otago shelf

glacial interglacial mis 1 10 migrations of the subtropical front across odp site 1119 canterbury bight southwest pacific ocean abstract ocean drilling program odp site 1119 is located at water depth 395 m near the subtropical front stf here represented by the southland front just downslope from the shelf edge of eastern south island new zealand the upper 86 19 metres composite depth mcd of site 1119 sediment was deposited at an average sedimentation rate of 34 cm kyr during marine isotope stages mis 1 8 0 252 ka and is underlain across a 25 kyr intra mis 8 unconformity by mis 8 5 11 277 367 ka and older sediment deposited at 14 cm kyr a time scale is assigned to site 1119 using radiocarbon dates for the period back to 39 ka and prior to then by matching its climatic record with that of the vostok ice core which it closely resembles four palaeoceanographic proxy measures for surface water masses vary together with the sandy muddy glacial interglacial g i cyclicity at the site interglacial intervals are characterised by heavy 13c high colour reflectance a proxy for carbonate content low ray a proxy for clay content and light 18o conversely glacial intervals exhibit light 13c low reflectance high ray and heavy 18o signatures early interglacial intervals are represented by silty clays with 10 105 cm thick beds of sharp based chondrites burrowed shelly graded fine sand the sands are rich in foraminifera and were deposited distant from the shoreline under the influence of longitudinal flow in relatively deep water glacial intervals comprise mostly micaceous silty clay though with some thin 2 10 cm thick sands present also at peak cold periods and contain the cold water scallop zygochlamys delicatula interglacial sandy intervals are characterised by relatively low sedimentation rates of 5 32 cm kyr cold climate intervals mis 10 6 and 2 have successively higher sedimentation rates of 45 69 and 140 cm kyr counter intuitively and forced by the bathymetric control of a laterally moving shoreline during g i and i g transitions the 1119 core records a southeasterly seaward movement of the stf during early glacial periods accompanied by the incursion of subtropical water stw above the site and northwesterly landward movement during late glacial and interglacial times resulting in a dominant influence then of subantarctic surface water saw the history of passage of these different water masses at the site is clearly delineated by their characteristic 13c values the intervals of thin graded sands muds which occur within mis 2 3 6 7 4 and 10 indicate the onset at times of peak cold of intermittent bottom currents caused by strengthened and expanded frontal flows along the stf which at such times lay near site 1119 in close proximity to seaward encroaching subantarctic waters within the bounty gyre in common with other nearby southern hemisphere records the cold period which represents the last glacial maximum lasted between 23 18 ka at site 1119 during which time the stf and subantarctic front saf probably merged into a single intense frontal zone around the head of the adjacent bounty trough

displacement since the pliocene along the southern section of the alpine fault new zealand relocation of a fiordland derived pliocene conglomerate halfway formation that is currently exposed 100 km northeast of its source area indicates that the average displacement rate on the alpine fault new zealand since the pliocene must have been 27 4 mm yr and probably 35 5 mm yr this represents at least three quarters of the currently predicted plate velocity and indicates that a high proportion of plate motion in the region has been partitioned along the alpine fault since the pliocene these results combined with the apparent absence of major displacement on the alpine fault for at least the past 250 yr indicate that a large earthquake may be due the provenance of the halfway formation also allows crude estimates of uplift since the pliocene of 200 800 m for the west coast cascade valley and 1 6 km for western fiordland

significant increase in relief of the european alps during mid pleistocene glaciations the effect of expanded glaciation on the relief of mountain ranges is debated chronometric and model data from the european alps suggest that relief in the rhone valley was enhanced as a result of the increased incision of the valley following the mid pleistocene climate transition

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

effect of cenozoic ice sheet fluctuations in antarctica on the stratigraphic signature of the neogene stratigraphic successions from the gulf of mexico offshore alabama northeast java indonesia ross sea antarctica and several other continental margins have been examined all are characterized by very similar neogene stratal geometries in seismic profiles and well log cross sections from these areas a large mid oligocene i e latest early oligocene earliest late oligocene basinward shift in coastal onlap is followed by a major early miocene transgression and aggradation which is in turn followed by early middle miocene transgressions and late middle and late miocene progradational episodes the succession culminates in plio pleistocene high frequency progradations and transgressions the interregional character of the neogene stratal signature and its similarity to the stratal geometry found in seismic data from the ross sea continental shelf antarctica suggest that the neogene stratal signature is a manifestation of glacioeustatic fluctuations a review of the literature and an analysis of recently acquired and published data indicate that the first major ice sheet grounding event in the ross sea occurred during middle to late oligoce time the ross sea is the repository for ice flowing from a major portion of the continental interior thus the glacial record of the ross sea should serve as a gage of ice volume changes on the continent that were large enough to influence global eustasy the ice advance onto the ross sea continental shelf during middle to late oligocene time may have been the result of a decrease in the rate of shelf subsidence as rifting in the ross sea slowed or ceased advance of the ice sheet resulted in widespread erosion of the continental shelf and shelf overdeepening it is hypothesized that metastable marine based ice sheets have waxed and waned on the antarctic continental shelf since at least the oligocene and that the these waxing and waning events were responsible for the development of a global neogene stratigraphic signature

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

sedimentary sequences in the gulf of lion a record of 100 000 years climatic cycles abstract the wide continental shelf of the gulf of lion up to 70 km has been the object of numerous investigations since the early days of oceanography yet the question of sequences duration the mechanisms of deposition and factors implied remained unanswered a study of a very dense grid of very high resolution vhr seismic reflection sparker data associated with surficial cores both collected by ifremer between 1992 and 2001 on the outer shelf and upper slope offshore of sete in the languedoc region gives a new insight into these issues analysis of the 3d geometry of the sedimentary record reveals a basic depositional pattern consisting of a pair of horizontally juxtaposed and downlapping prisms prism pi with low angle clinoforms results obtained from integrating lithology palynology micropaleontology seismic stratigraphy stratigraphic simulation support the hypothesis that the basic depositional pattern records a 100 000 years glacioeustatic interglacial glacial cycle as previously suggested by aloisi aloisi j c 1986 sur un modele de sedimentation deltaique contribution a la connaissance des marges passive these de doctorat d etat universite de perpignan 162 pp prisms pi corresponds to deposition at high sea level and prisms pii to deposition during low sea level at glacial maxima five sequences of paired prisms capped by five major erosion surfaces have been identified and modelled showing that the corresponding glacioeustatic cycles the last five cycles at least are recorded on the shelf of the western part of the gulf of lion

ni cu au and platinum group element contents of sulphides associated with intraplate magmatism a synthesis the tectonic setting of intraplate magmas typically a plume intersecting a rift is ideal for the development of ni cu platinum group element bearing sulphides the plume transports metal rich magmas close to the mantle crust boundary the interaction of the rift and plume permits rapid transport of the magma into the crust thus ensuring that no sulphides are lost from the magma en route to the crust the rift may contain sediments which could provide the sulphur necessary to bring about sulphide saturation in the magmas the plume provides large volumes of mafic magma thus any sulphides that form can collect metals from a large volume of magma and consequently the sulphides will be metal rich the large volume of magma provides sufficient heat to release large quantities of s from the crust thus providing sufficient s to form a large sulphide deposit the composition of the sulphides varies on a number of scales i there is a variation between geographic areas in which sulphides from the noril

potentially active faults in the rapidly eroding landscape adjacent to the alpine fault central southern alps new zealand 1 potentially active faults are exposed in the steep glaciated topography of the central southern alps new zealand immediately adjacent to the alpine fault plate boundary four major faults exposed along the flanks of three of the highest mountain ranges strike 10 23 km potentially 40 km nne oblique to the alpine fault dipping 57 12 nw in the opposite direction youngest discernable motions were reverse dip slip accommodating both margin perpendicular shortening and dextral margin parallel components of plate motion kinematic analysis yields a compression axis 295 10 9 trend or plunge equivalent to the contemporary shortening determined from seismological and geodetic studies suggesting the faults may be active although definitive evidence for recent movement or single event displacements is lacking there are 106 other potentially active faults mapped in central southern alps with strike lengths 4 73 km earthquake parameters were assigned from fault trace lengths and historical earthquake statistics indicating potential for mw 5 5 7 4 earthquakes at recurrence intervals of 1000 10 000 years such long recurrence intervals are consistent with the faults having little surface expression with rapid erosion of these seismically agitated mountains erasing any evidence of surface rupture during periods between earthquakes the central southern alps faults exemplify the difficulty in fully deciphering long term e g holocene or quaternary records of seismicity in tectonically active regions with rapidly evolving landscapes although there may be little evidence of surface ruptures remaining in the landscape the faults are still an important potential source of earthquakes and seismic hazard

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

high frequency sea level and sediment supply fluctuations during termination i an integrated sequence stratigraphy and modeling approach from the adriatic sea central mediterranean abstract after the end of the last glacial maximum lgm termination i recorded one of the fastest and highest amplitude eustatic oscillations of the late quaternary in less then 15 kyr between ca 20 and 5 5 kyr cal bp sea level rose 120 m with at least two steps of increased rate of ice melting and eustatic rise named meltwater pulses 1a and 1b the transgressive sedimentary succession deposited during this interval on several mid latitude continental margins among which the central adriatic margin includes three distinct units each deposited during a specific interval of the last sea level rise in particular the central adriatic middle tst unit mtst composed of two prograding sedimentary wedges separated by an erosional surface appears the most complex of the three tst units the mtst unit formed during an interval of extreme climatic instability including the bolling allerod and the younger dryas holocene transition sequence stratigraphy analyses integrated by core samples and 14c age estimates indicate an enhanced sediment flux during the deposition of the mtst unit as a consequence of high frequency climatic oscillations model simulations with hydrotrend v3 0 a hydrological water balance and transport model show high rates of sediment delivery within the interval between 13 8 and 11 5 kyr cal bp as a consequence of increased rates of rainfall and partial melting of the alpine glaciers reconstructions of the sediment architecture using 2d sedflux 1 0c a basin fill model reproduce the complexity of the internal architecture of the middle tst unit driven primarily by sea level the internal unconformity within the mtst unit can best be explained by introducing a minor sea level fall during the younger dryas this conclusion is supported by the presence of an extensive barrier island lagoon system at 75 m below present sea level corresponding to the younger dryas time interval and representing the best evidence of paleo shoreline for this interval

the glacial sedimentology and geomorphological evolution of an outwash head moraine dammed lake south island new zealand extensive exposures through the glacial landforms around southern lake pukaki new zealand comprise seven lithofacies lfs 1 7 lfs 1 3 are grouped together as lfa 1 pukaki member and record pulsed subaqueous grounding line fan progradation cohesionless debris flows underflow activity and rhythmite deposition by suspension settling iceberg rafting of dropstones and pulsed traction current activity localized disturbance of these deposits by glacitectonic deformation and multi generational hydrofracture fills records minor readvances by the glacier snout and the emplacement of a glacitectonite lf 4 derived from cannibalization of glacilacustrine sediments lfs 4 6 are grouped together as lfa 2 twizel member and record direct glacigenic deposition of glacitectonite lf 4 subglacial traction till lf 5 and supraglacially dumped boulder rubble lf 6 stratigraphic relationships between lfa 1 with lfa 2 record the oscillatory behaviour of the former tasman glacier snout when it formed a calving margin in a proglacial and locally supraglacial lake dammed by a glacitectonically disturbed outwash head and lateral moraine ridges this is entirely consistent with the landform sediment record of its coeval terrestrial margins where flutings and push moraines are diagnostic of active temperate glacier recession from a glacially overridden outwash head the latter being recorded by the vertically stacked sub horizontally bedded and coarse grained gravels of lf 7 waitaki member previous proposals that late pleistocene lake damming was initiated by an ice cored moraine arc appear unfounded because the glacilacustrine deposits only lie above the altitude of the outwash head lateral moraine arc in locations where they have been glacitectonically compressed alternatively it is proposed that the overdeepened subglacial topography was produced by the construction of an outwash head leading to a glacilacustrine sediment sink which operates at times when the expanded tasman glacier actively retreats from the outwash head apex the changing landsystem imprint related to the shrinkage of the tasman glacier records spatio temporal landsystem change involving evolution from a coupled landsystem to a moraine dammed to an uncoupled landsystem

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

chemical and physical weathering in new zealand s southern alps monitored by bedload sediment major element composition abstract the haast and clutha rivers drain opposing flanks of new zealand s southern alps major element analyses of grain size fractions 2 1 mm 1 mm 355 m 355 63 m and 2 o 5 concentrations in all river sediment suggests that most cao is bound in a combination of phosphate bearing minerals such as apatite along with other heavy mineral phases with similar hydrodynamic properties e g epidote chemical index of alteration cia values for grain size fractions from both rivers are similar haast 54 63 clutha 49 61 and do not systematically vary with grain size or sample location al 2 o 3 cao na 2 o k 2 o a cn k relationships suggest that cia values are controlled by albite muscovite mixing rather than feldspar weathering both a cn k relationships and modal mineralogical calculations from clutha river samples indicate progressive downstream attrition of muscovite from coarser to finer grain size fractions in contrast haast river sediments display less variable normative muscovite concentrations and no downstream enrichment depletion trends the haast and clutha watersheds have drastically different sediment yields but the similarity of sediments from both rivers indicates that there is minimal climatic control on the weathering intensity of fluvial sediments rather bedload geochemistry is controlled primarily by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite albite quartz the geochemical signature of mechanical attrition and hydrodynamic winnowing is more developed in clutha river samples because of longer sediment residence time within its fluvial system these findings suggest that high standing island hsi fluvial sedimentary evolution is characterized by the dominance of physical weathering processes and the absence of silicate chemical weathering signatures

quantitative mineralogy of the yukon river system changes with reach and season and determining sediment provenance the mineralogy of yukon river basin sediment has been studied by quantitative x ray diffraction bed beach bar and suspended sediments were analyzed using the rockjock computer program the bed sediments were collected from the main stem and from selected tributaries during a single trip down river from whitehorse to the yukon river delta during the summer of 2001 beach and bar sediments were collected from the confluence region of the tanana and yukon rivers during the summer of 2003 suspended sediments were collected at three stations on the yukon river and from a single station on the tanana river at various times during the summers of 2001 through 2003 with the most complete set of samples collected during the summer of 2002 changes in mineralogy of yukon river bed sediments are related to sediment dilution or concentration effects from tributary sediment and to chemical weathering during transport carbonate minerals compose about 2 wt of the bed sediments near whitehorse but increase to 14 wt with the entry of the white river tributary above dawson thereafter the proportion of carbonate minerals decreases downstream to values of about 1 to 7 wt near the mouth of the yukon river quartz and feldspar contents of bed sediments vary greatly with the introduction of pelly river and white river sediments but thereafter either increase irregularly quartz from 20 to about 50 wt or remain relatively constant feldspar at about 35 wt with distance downstream clay mineral content increases irregularly downstream from about 15 to about 30 wt the chief clay mineral is chlorite followed by illite smectite there is little to no kaolinite the total organic carbon content of the bed sediments remains relatively constant with distance for the main stem generally 1 to 2 wt with one exception but fluctuates for the tributaries 1 to 6 wt the mineralogies of the suspended sediments and sediment flow data were used to calculate the amount of mineral dissolution during transport between eagle and pilot station a distance of over 2000 km we estimate that approximately 3 wt of the quartz 15 wt of the feldspar 1 wt of the alkali and 25 wt of the plagioclase and 26 wt of the carbonates 31 wt of the calcite and 15 wt of the dolomite carried by the river dissolve in this reach the mineralogies of the suspended sediments change with the season for example during the summer of 2002 the quartz content varied by 20 wt with a minimum in mid summer the calcite content varied by a similar amount and had a maximum corresponding to the quartz minimum these modes are related to the relative amount of sediment flowing from the white river system which is relatively poor in quartz but rich in carbonate minerals suspended total clay minerals varied by as much as 25 wt with maxima in mid july and suspended feldspar varied up to 10 wt suspended sediment data from the summers of 2001 and 2003 support the 2002 trends a calculation technique was developed to determine the proportion of various sediment sources in a mixed sediment by unmixing its quantitative mineralogy results from this method indicate that at least three sediment sources can be identified quantitatively with good accuracy with this technique sediment mineralogies can be used to calculate the relative flux of sediment from different tributaries thereby identifying sediment provenance

across shelf sediment transport since the last glacial maximum southern california margin correlation of continental shelf slope stratigraphy in santa monica bay southern california with ocean drilling program records for nearby slope basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the last glacial maximum lgm marine flooding surfaces preserved in a transgressive sequence on the santa monica shelf provide a key link between base level elevation and sediment transport across shelf sediment accumulation rates at slope basin sites were maximal ca 15 10 ka well after the lgm decreased during the 12 9 ka transition from fluvial estuarine to fully marine conditions on the shelf and decelerated throughout the holocene to 30 75 of their values at the lgm the deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca 13 ka as predicted by sequence stratigraphic models however the records make clear that factors other than base level modulated slope basin accumulation rates during the deglaciation

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

response of surface water masses and circulation to late quaternary climate change east of new zealand a series of cores from east of new zealand have been examined to determine the paleoceanographic history of the late quaternary in the sw pacific using planktonic foraminiferal data distinct shifts of species can be seen between glacial and interglacial times especially south of chatham rise east of south island foraminiferal fragmentation ratios and benthic planktonic foraminiferal ratios both show increased dissolution during glacials especially isotope stage 2 to the south of chatham rise the present day subtropical convergence appears to be tied to the chatham rise at 44 s but during glacial times this rise separated cold water to the south from much warmer water to the north with an associated strong thermal gradient across the rise we estimate that this gradient could have presented as much as an 8 c temperature change across 4 of latitude during the maximum of the last ice age there is only weak evidence of the younger dryas cool event but there is a clear climatic optimum between 8 and 6 4 ka with temperatures 1 2 c higher than the present day the marine changes compare well with vegetational changes on both south and north island

glacially influenced late pleistocene stratigraphy of a passive margin new jersey s record of the north american ice sheet abstract glacial isostasy and the sediment supply changes associated with the waxing and waning of ice sheets have dramatic effects on the stratigraphy of adjacent continental shelves in ancient stratigraphic records the glacial influences on such deposits could be difficult to recognize because of the removal of coeval terrestrial glacial deposits by erosion this study illustrates the effects of the laurentide ice sheet on a basin near its maximum limit the new jersey continental shelf analysis of 1600 km of geopulse uniboom minisparker and airgun profiles reveals four depositional sequences that have a maximum thickness of 75 m near the shelf edge sequences i and iv correspond to the major glacial interglacial sea level changes at marine isotope chron mic 6 5e and 2 1 whereas sequences ii and iii reflect smaller scale sea level fluctuations during chrons 4 3c and 3b 3a respectively sequences i and iv are characterized by relatively thick low stand to early transgressive deposits near the shelf edge formed during times of increased sediment supply but are thin and discontinuous across much of the shelf reflection horizons in these units deepen northward in the northern half of the study area due to collapse of a peripheral bulge that formed at the margin of the laurentide ice sheet the hudson river moved from a more southerly drainage pattern to the modern hudson shelf valley position possibly under the influence of the advancing peripheral bulge sequences ii and iii are largely preserved within a broad mid shelf swale likely created by the migration of an ancestral hudson river and their thickness implies much higher sedimentation rates during chrons 4 and 3 than seen today if the terrestrial glacial record was eroded the increased rates of sedimentation during the pleistocene dominance of sediments derived from northern new england and northward tilting of strata could be interpreted as a result of uplift of a northern source area the unusually high frequency of the relative sea level oscillations 20 kyr the concentration of sediment supply during low stands and early transgressions and the correspondence of sea level change with climatic change could be used to infer their relationship to a nearby ice sheet geologists studying deposits formed during times of widespread continental glaciation should consider possible glacial influences on the stratigraphy of mid latitude deposits even in the absence of sediments directly deposited by ice

new zealand maritime glaciation millennial scale southern climate change since 3 9 ma ocean drilling program site 1119 is ideally located to intercept discharges of sediment from the mid latitude glaciers of the new zealand southern alps the natural gamma ray signal from the site s sediment core contains a history of the south island mountain ice cap since 3 9 million years ago ma the younger record to 0 37 ma resembles the climatic history of antarctica as manifested by the vostok ice core beyond and back to the late pliocene the record may serve as a proxy for both mid latitude and antarctic polar plateau air temperature the gamma ray signal which is atmospheric also resembles the ocean climate history represented by oxygen isotope time series

stratigraphic architecture and spatio temporal variability of high frequency milankovitch depositional cycles on modern continental margins an overview abstract this study is a review of quaternary milankovitch cycles as recorded on modern continental shelves worldwide on the background of the many existing examples we focus on selected case studies from mediterranean adriatic and tyrrhenian seas and atlantic gulfs of mexico and cadiz margins that represent general and peculiar characters of middle upper pleistocene sequences forming under the control of composite 100 and 20 ka milankovitch cycles the most pervasive stratigraphic pattern displayed by shelf deposits is referred to the 100 ka sea level cycle and consists of fairly uniform depositional sequences mostly composed by regressive deposits forming during the falling limb of the sea level curve these are generally classified as falling stage systems tract fsst and display a regressive facies architecture reflecting the dominant control of sea level on many margins fsst units may show slight though significant differences with respect to highstand systems tract hst and lowstand systems tract lst regressive units more closely reflecting environmental changes and the local variability of depositional systems in contrast with the theoretical and overall scale independent model developed to predict composite stratigraphic cycles and sequences the middle upper pleistocene stratigraphic record from numerous shelf settings shows a subdued signature of the higher frequency 20 ka milankovitch cyclicity however when detectable the 20 ka architectural pattern is characterized by a relatively greater spatial and temporal variability compared to 100 ka sequences this fact likely reflects the increasing importance of factors controlling the depositional environment e g seafloor morphology oceanographic regime sediment input and dispersal etc with respect to sea level change during the shorter intervals encompassed by 20 ka cycles on this basis two end member cases have been distinguished depending on the generation or not of high frequency sequence boundaries a prerequisite to qualify the higher frequency motifs as depositional sequences these two end members are comprehensive of the highly variable patterns displayed by middle upper pleistocene shelf sequences which in turn reflect the interplay between the geological setting the dominant sea level control and the effective response of sedimentary systems the variable stratigraphic patterns of milankovitch cycles represent conceptual and practical constraints as to the classification of high frequency quaternary sequences under the general schemes of the standard sequence stratigraphy model

glacial to interglacial changes in non carbonate and carbonate accumulation in the sw pacific ocean new zealand abstract fluxes of carbonate and non carbonate terrigenous biogenic siliceous sediment back to a maximum of marine isotope stage mis 6 were determined for 54 cores from off eastern new zealand mass accumulation rates mars were derived using dry bulk densities measured directly from fresh cores or in the case of dry archived samples on estimates from a density carbonate relationship mars exhibit wide spatial and temporal variability in response to i the location of cores relative to the terrigenous source of new zealand current pathways and local oceanographic features and ii palaeoclimatic change for mis 1 2 non carbonate accumulated at a high rate between 27 and 18 ka calendar years due to an influx of waterborne and aeolian terrigenous detritus together with localised production of biogenic silica under a northward intrusion of subantarctic waters and an increase in wind induced upwelling by 18 12 ka non carbonate mars reduced as winds ameliorated and sea level rose to confine some of the terrigenous load to the continental shelf the holocene transgression was accompanied by warmer sea surface temperatures the formation of coastal and lacustrine sediment traps and more widespread terrestrial vegetation these conditions further reduced the deep oceanic non carbonate flux to levels about half those of glacial periods in contrast carbonate mars were lower in cold periods reflecting lower productivity increased dissolution and in the case of the generally productive waters of chatham rise to redistribution by bottom currents however off central new zealand carbonate production was higher on the continental margin possibly because of enhanced upwelling under the strong wind regime of mis 2 such localised effects produced glacial carbonate mars higher than interglacial mis 1 values for the rest of the region carbonate fluxes increased to an early to middle mis 1 maximum before generally declining in recent times

near synchroneity of new zealand alpine glaciations and northern hemisphere continental glaciations during the past 750 kyr the brunhes magnetochron 0 730 kyr at deep sea drilling project site 594 off eastern south island new zealand comprises up to 100 m of alternating units of pelagic and hemipelagic ooze formed during interglacial and glacial periods respectively the youngest hemipelagic interval corresponds to glacial isotope stage 2 and can be correlated with extensive glacial and glacio fluvial deposits of the late last glaciation 27 13 kyr bp on south island inferring the same genetic link for the other hemipelagic sediment units down core we show here that as many as 12 major episodes of expanded alpine glaciation have occurred on south island in the past 730 kyr each of these glacial episodes coincided with a period of significant 18o enrichment 2 in the core resulting from changes in ocean isotope composition associated with major growth phases of the northern hemisphere ice sheets the inferred history of alpine glaciations on this remote south pacific island appears to be closely phase locked 3 kyr to world wide climate changes

carbonate depositional sequence development on active fault blocks the albian in the castro urdiales area northern spain the aptian to lowermost albian carbonate platform of castro urdiales cantabria northern spain was broken up by extensional tectonic movements shortly after the beginning of the albian block faulting characterized this rifting episode the effects of which waned during the albian in crestal locations tilting of the fault blocks caused the subaerial exposure of parts of the older platform resulting in intense karst diagenesis differential subsidence of the blocks controlled the development of a crestal residual carbonate platform arenillas which was surrounded by deeper water on both sides seven unconformities related to platform exposure and karstification are identified on the arenillas platform and form the basal boundaries of seven depositional sequences s1 s7 on the platform lowstand systems tract deposits consist of breccias filling caves and grainstones and debris flow deposits filling incised canyons transgressive plus highstand systems tracts consist of rare marls plus shallow water rudistid coral and chondrodontid limestones in the basin the unconformities are erosional surfaces at the base of resedimented limestones marls or sandy or silty siliciclastics lowstand systems tracts transgressive plus highstand systems tracts in this setting consist of marls and hemipelagic marly limestones tectonism is believed to be the main control on sequence formation and only a few sequence boundaries e g the base of s6 in the upper albian inflatum zone can be correlated with eustatic events

eustatic and tectonic control on deposition and lateral variability of quaternary regressive sequences in the adriatic basin italy abstract during the late pleistocene sea level variations related to glacio eustatic cycles induced the deposition of four regressive sequences on the western continental shelf of the adriatic basin the four sequences are bounded by erosion surfaces that formed during sea level fall sub aerial exposure of the shelf and subsequent sea level rise and erosional reworking the sequences and the erosion surfaces at their top numbered 1 4 top down are correlated on distances in the order of 300 km in the central and south adriatic core control on deposits of the most recent depositional sequence sequence 1 suggests that each sequence records a fourth order ca 100 120 kyr cyclicity of sea level change within each depositional sequence progradational units representing highstand to forced regression are dominant whereas transgressive deposits are absent or reduced in both thickness and lateral extent sequences are thus referred to as regressive sequences deposition during sea level fall occurred on an overall subsiding shelf through the dispersal of fine grained sediment supplied from the adjacent alpine and apennine chains this resulted in stacked forced regression deposits thick enough to survive complete removal during subsequent phases of sub aerial and marine erosion erosion and or non deposition were enhanced only where tectonic uplift and morphological highs further reduced the remaining accommodation space resulting in local thickness reduction or in the non preservation of the regressive sequences at larger scale thickness variability and depocenter distribution north and south of the gargano promontory an uplifted block bisecting the adriatic foreland reflect differential deposition and preservation of regressive deposits as a function of contrasting tectonic setting and resulting physiography of the shelf and upper slope

wave enhanced sediment gravity flows and mud dispersal across continental shelves reappraising sediment transport processes operating in ancient mudstone successions recent studies of marine shelf sediment dispersal show that wave enhanced sediment gravity flows are widespread phenomena and can transport large volumes of fluid mud rapidly across low gradient shelves flow evolution is controlled by sediment supply seabed gradient and spatial distribution of wave energy at the seabed using existing flow models we predict that such flows in mud dominated sediments will develop a three part microstratigraphy produced by changing flow conditions beginning with wave induced turbulent resuspension then development of a wave enhanced sediment gravity flow prior to lutocline collapse and suspension settling petrographic examination of modern flow deposits collected from the eel shelf reveals that resultant beds possess a microstratigraphy consistent with our hypothesis a silt rich basal subunit with curved ripple laminae abruptly overlain by a subunit composed of continuous intercalated silt clay laminae and an upper clay rich drape analyses of beds from ancient mud rich outer shelf and basinal successions cleveland ironstone jurassic uk and mowry shale cretaceous united states show that they too contain beds with this three part organization suggesting that such flows were active in these ancient settings too recognition of these microstructures in these ancient mud dominated successions demonstrates that sediment in these settings was commonly reworked and transported advectively downslope by high energy events contrasting with previous interpretations of these units that deposition was dominated by quiescent suspension settling identification of these recognition criteria now allows the products of this newly recognized sediment dispersal mechanism to be identified in other shale dominated successions

glaciations in response to climate variations preconditioned by evolving topography landscapes modified by glacial erosion show a distinct distribution of surface area with elevation hypsometry in particular the height of these regions is influenced by climatic gradients controlling the altitude where glacial and periglacial processes are the most active and as a result surface area is focused just below the snowline altitude yet the effect of this distinct glacial hypsometric signature on glacial extent and therefore on continued glacial erosion has not previously been examined here we show how this topographic configuration influences the climatic sensitivity of alpine glaciers and how the development of a glacial hypsometric distribution influences the intensity of glaciations on timescales of more than a few glacial cycles we find that the relationship between variations in climate and the resulting variation in areal extent of glaciation changes drastically with the degree of glacial modification in the landscape first in landscapes with novel glaciations a nearly linear relationship between climate and glacial area exists second in previously glaciated landscapes with extensive area at a similar elevation highly nonlinear and rapid glacial expansions occur with minimal climate forcing once the snowline reaches the hypsometric maximum our results also show that erosion associated with glaciations before the mid pleistocene transition at around 950 000 years ago probably preconditioned the landscape producing glacial landforms and hypsometric maxima such that ongoing cooling led to a significant change in glacial extent and erosion resulting in more extensive glaciations and valley deepening in the late pleistocene epoch we thus provide a mechanism that explains previous observations from exposure dating and low temperature thermochronology in the european alps and suggest that there is a strong topographic control on the most recent quaternary period glaciations