sea level changes in a back arc foreland transition the late carboniferous permian karoo basin of south africa abstract the late carboniferous to early permian succession in the karoo basin consists in ascending stratigraphic order of diamictites mudrocks greywackes and immature sandstones the diamictites are interpreted as glacigene deposits laid down by a marine ice sheet on a shelf post glacial suspension settling of predominantly mud occurred on the basin floor during open marine and later brackish conditions basin floor fan deposits accumulated in the foredeep whereas deltaic mud silt and sand finally infilled the basin glacigene sedimentation occurred in a back arc basin during the late carboniferous and early permian the post glacial succession accumulated in a foreland basin in which the rising orogenic belt was the predominant sediment source relative sea levels following the major namurian regression apparently remained low during the extensive gondwana glaciation marine ice sheets are highly sensitive to sea level fluctuations and minor sea level rises probably climatically controlled were recorded as interglacials when parts of the marine ice sheet collapsed final collapse of the marine ice sheet was associated with a major transgression post glacial mudrock deposition was characterised by relatively high sea levels except for the period of basin floor fan deposition when there was a sea level lowstand final infilling of the basin by prograding deltas was accompanied by a major regression the late carboniferous to early permian sea level fluctuations in the karoo basin show correspondence with global eustatic cycles reflecting low tectonic interference with sea level patterns however late permian sea levels were predominantly tectonically controlled as a result of foreland basin evolution possible global eustatic events complemented apparent sea level changes within the basin during this period

kaikoura canyon new zealand active conduit from near shore sediment zones to trench axis channel kaikoura canyon is one of a few major active conduits between a near shore sediment transport system and a deep ocean channel it is the sink for mobile zones of gravel sand and mud that migrate northwards off northeastern south island new zealand it is presently the primary source for the 1500 km long hikurangi channel which supplies overbank turbidites to a filled trench an ocean plateau basin and a distal fan drift swath data seismic profiles side scan sonographs aerial photographs cores grab samples and current meter data are used to define the shape and texture of the canyon and adjacent shelf in order to better understand how coastal processes and canyon interact to supply sediment to the deep ocean kaikoura canyon is 60 km long up to 1200 m deep and generally u shaped in profile its head is within 500 m of the shore and within 200 m of rocky projections from the shore platform in a mountain backed bay without large rivers the canyon head incises the 18 m depth contour and boulders pebble gravel and megarippled coarse sand reach the canyon rim fine sand migrating northward along the shelf under the influence of waves and currents is trapped in a southward projecting canyon head gully which incises the thickest part of the holocene sediment prism it is estimated that about 1 5 106 m3 of sediment falls into the canyon head each year tensional fractures around the canyon rim suggest that sediments in the canyon head gully are unstable gravel turbidites with post last glacial age shells are at or near the seabed in the lower canyon but are blanketed by many thin silt and sand possibly storm generated turbidites in the upper canyon the top gravel contains a twig that is about 170 years old suggesting that the last major collapse in the canyon head coincides with many onshore rockfalls triggered by rupture of a major strike slip plate boundary fault in about 1833 an underlying gravel is about 300 years old and may again coincide with fault rupture most of the large earthquake triggered failures may ignite to form self perpetuating autosuspension flows that feed a 1500 km long deep sea turbidite channel

geomorphology of lake lisan terraces along the eastern coast of the dead sea jordan abstract lake lisan the lake that filled the jordan graben during the last glacial left behind a well developed sequence of erosional and depositional shore terraces in the south east of the current dead sea these terraces record a series of stillstands that were caused by small transgressions within an overall trend of falling lake levels the terraces were observed in places where they had not been identified previously the morphology of the terraces was investigated in six cross sections using differential gps altimetry the levels of the terraces range between 370 and 148 m a s l the high stand of lake lisan at 148 m correlates well with the high level of 150 m reported by bowman and gross bowman d gross t 1992 the highest stand of lake lisan 150 meters below msl israel journal of earth science 41 233 237 along the western coast of lake lisan the lake terraces are horizontal elongated and tectonically undisturbed and have a sub horizontal foreshore tread with an average slope of 8 2 and steep backshore cliff riser with an average slope of 17 7 the six cross sections show a good altitudinal correlation between their terraces moreover the terraces appear in undisturbed continuity on the aerial photos these morphological characteristics demonstrate that the retreat of the lake was a result of substantial climatic changes not of tectonic subsidence in situ stromatolites were found on most of the terraces reflecting a shallow water environment and emphasizing that these terraces are recessional well developed desert varnish and tafoni observed on blocks sitting on the terrace surfaces imply a long period of exposure and a low rate of post lacustrine erosion the formation of lisan terraces is constrained mainly by coastal slope water depth and underlying lithology the morphological analysis of these terraces allows identification of two kinds of pseudo terraces which were formed as a result of tread or riser destruction u th and osl dating allowed the dating of three events within the lake level curve more precisely the high level of 148 m occurred at 30 5 0 22 ka bp consistent with the heinrich event 3 and dansgaard oeschger stadial 5 the coldest period in the ngrip greenland ice core record the next lower terrace at 154 m was formed at 22 9 ka bp 0 29 and corresponds to the stadial 2c the final phase of the last high glacial the correlation between the lisan high stands and climatic stadials suggests that northern hemispheric cold periods led to periods with a more positive water balance in the near east at 10 0 8 ka bp lake lisan experienced a sharp drop to 200 m followed by a transgression between 9 5 to 7 ka bp

sea level control of stacked late quaternary coastal sequences central great barrier reef lithofacies analysis pollen assemblages and radiocarbon age dates of 20 stratigraphic drill holes are used to develop an evolutionary history for late quaternary sedimentation in two coastal embayments landward of the central great barrier reef different physiographic settings of the embayments result in two contrasting styles of sedimentary sequence a an exposed moderate energy beach barrier lagoon system wyvuri embayment and b a protected low energy muddy inlet fill sequence mutchero inlet despite sharp contrast in sequence style similar depositional cycles occur in both embayments in response to late quaternary sea level fluctuations including 1 a last interglacial highstand 2 m c 125 000 yr bp beach barrier wyvuri 2 an early to mid holocene 8000 6100 yr bp transgressive beach barrierlagoon wyvuri and estuarine infill mutchero and 3 mid holocene to present highstand beach barrier wyvuri and estuarine mutchero progradation preservation of such cycles in the stratigraphic record would produce a series of vertically stacked and offset linear barrier sands surrounded by lagoonal mud and fine grained shoreface sediment juxtaposed to muddy estuarine infills sea level elevations are well recorded by the upward transition from rhizaghoru dominated intertidal mangrove mud to freshwater swamp clearly identified by pollen analysis and by the basal contacts of beach barrier sediments which sharply overlie the upper shoreface transgressive sedimentation is interrupted in both embayments by a constructional beach barrier wyvuri and abbreviated progradation mutchero corresponding to a 5 m pause in relative sea level rise at c 6800 yr bp sea level control of fine scale coastal sedimentation patterns is beginning to be widely recognized and provides an accurate analogue for stacked ancient sequences

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

tidal and sedimentary response to the late quaternary closure and opening of cook strait new zealand results from numerical modeling evidence from numerical modeling of the m2 tide supplemented by geological data reveals marked changes in the tidal and sedimentary regimes of cook strait over the last postglacial rise in sea level approximately 18 000 years b p when sea level was approximately 113 m the strait was reduced to a narrow bay by the emergence of a land bridge connecting the north and south islands of new zealand high sediment supply and low tidally induced bottom stress encouraged widespread deposition of fine sediment except at the bay mouth the narrows where localized high stress resulted in the transport of sediment to the deep ocean via cook strait canyons at 17 000 years b p approximately 88 m the bay reached maximum size and was near resonance with the oceanic tide resulting in high tidal amplitudes bottom stress and sediment movement at the narrows and bay head the land bridge was breached and cook strait was formed about 15 000 years b p approximately 75 m both the narrows and breach were subject to high bottom stress whereas the intervening area was a zone of convergent low stress and fine sediment deposition by 11 000 years b p approximately 40 m cook strait was well established and had a tidal response similar to the modern strait the rising sea levels inundated remnants of the land bridge to form the broad continental shelf approaches to cook strait today overall tidal stress is reduced and mud deposition prevails except on the inner shelf where periodic forcing by wind induced currents maintains a sandy substrate and in the narrows where a tidal phase difference of approximately 120 maintains a zone of high sediment movement

deglacial warming of the northeastern atlantic ocean correlation with the paleoclimatic evolution of the european continent abstract isotopic micropaleontologic and pollen analyses of deep sea cores from the bay of biscay and the northeastern atlantic ocean show that the deglacial warming of this oceanic area was closely correlated with the paleoclimatic evolution of the adjacent european continent temperatures were at least as warm as those of today in the bay of biscay between 13 300 and 11 000 b p coinciding with the combined bolling allerod warm continental events a major spread of polar water occurred between 11 000 and 10 000 b p during this event which coincides with the younger dryas continental cold event marine temperatures were almost as low as those of the last glacial maximum the final deglacial warming of the norteastern atlatntic ocean occurred during the following 3000 yr

to the islands born the research potential of submerged landscapes and human habitation sites from the islands of nw australia this paper focuses on the continental shelf of nw australia and on models for change in littoral and offshore environments of relevance to human occupation over the last 50 kyr major island groups occur on the shelf including the montebello and barrow islands and those of the dampier archipelago at lowest sea level around 22 ka these would have been uplands that then became progressively isolated by subsequent sea level rise by integrating archaeological and zooarchaeological records from excavations on these islands with the geology and geomorphology we interpret palaeoeconomic resource potential in relation to changing sea level and coastline morphology the preservation potential for submerged archaeological sites and features is also assessed current archaeological evidence from these offshore islands indicates that the submerged coastal landscape is likely to have been a potentially rich environment for resources and human occupation even at times of lowest sea level and regional aridity should any exploration of submerged archaeology be carried out in this region it is likely to be rewarding offering unique insights into late pleistocene coastal occupation

modern and ancient zygochlamys delicatula shellbeds in new zealand and their sequence stratigraphic implications the scallop zygochlamys delicatula is an indicator species for a carbonate shellground facies which occurs on the sediment starved outer shelf and upper slope around southern new zealand the modern distribution of z delicatula is restricted to areas where sea summer surface temperatures are less than ca 15oc its occurrence in late pliocene and pleistocene strata in north island has therefore been taken to indicate a northward expanded range during former glacial intervals we describe the sequence stratigraphic setting of examples of the z delicatula assemblage from the modern eastern south island shelf and from the plio pleistocene wanganui and mangaopari basins in north island we show that the z delicatula fauna occurs in both glacial and interglacial sediments and that its development requires the concurrence of cold water conditions and terrigenous sediment starvation these conditions occur most commonly at the transition between the transgressive and highstand systems tracts i e during rapid post glacial sea level rise and probable warming temperature however for palaeo locations below the contemporaneous lowstand shoreline z delicatula can also occur at the transition between the highstand and lowstand systems tracts i e during rapid post interglacial sea level fall and probable cooling temperature 1998 elsevier science b v all rights reserved

control of reservoir geometry and stratigraphic trapping by erosion surface e5 in the pembina carrot creek area upper cretaceous cardium formation alberta canada 1 seven major erosion e surfaces are found within the 100 m thick cardium formation in the subsurface of alberta erosion surface e5 has up to 20 m of erosional relief in the carrot creek area and is cut into originally horizontal open marine sandstones and mudstones the e5 surface has been correlated into the pembina area by construction of a structure map based on 2470 resistivity logs the e5 surface is characterized by a series of sub parallel southeast trending steps with lower areas between the steps this topography is interpreted to have formed during erosional shoreface retreat in a period of alternating transgression and stillstand of relative sea level tectonic tilting of the basin floor is also suggested by the topography of the erosion surface the tilti g is related to the accretion of exotic terranes and loading the continental margin the erosion surface is overlain by a continuous veneer of conglomerate interpreted as a transgressive lag this conglomerate thickens to 20 m in the lower areas at carrot creek where it is interpreted as a shoreface deposit rather than an offshore bar these shoreface conglomerates form important reservoirs the veneer also thickens to about 9 m in parts of pembina but the thick conglomerates occur not in the lows but on top of the steps reconstruction of the geometry of the steps indicates that at times of unusually high sediment supply during transgression conglomerates were deposited as local bars in the lower shoreface the sandstones and mudstones below the erosion surface at pembina shale out northeastward partly forming a stratigraphic trap however these sediments are also truncated by the e5 erosion surface and buried by transgressive mudstones these mudstones contribute significantly to updip stratigraphic trapping the long narrow sand body trends mapped in pembina and adjacent fields are due to the erosive dissection of an originally extensive and continuous sheet of interbedded sandstones and mudstones and not as has been suggested to an offshore bar origin for the fields

middle and late holocene sea levels along the israel mediterranean coast evidence from ancient water wells during the course of a study of historical water wells along the israeli shore which has been in progress since 1984 an innovative method for investigating sea level fluctuations was developed eighteen ancient water wells were re dug 14 by the author and four by archaeologists most of the re dug wells are found at archaeological sites located a very short distance inland from the present shoreline evidence of ancient ground water levels found in the wells directly reflects on historic eustatic sea level changes and the rate at which the end of the post glacial transgression advanced a critical question concerns the durability and life span of these wells as the true age is very important for the accurate reconstruction of a sea level curve the pre pottery neolithic well of atlit yam which is the oldest known well in the world ca 8000 yr old enabled the most accurate sea level reconstruction for early holocene times sea level rise during that period of the atlit yam site was of the order of 20 mm yr 1 at the beginning slowing to 6 8 mm yr 1 at the abandonment of this site at ca 7 5 ka bp when it was flooded by the advancing and rising sea after reaching its present level sea level fluctuations for the past 2 5 millennia were not greater than 1 5 to 2 m 1997 john wiley sons ltd

sequence architecture during the holocene transgression an example from the great barrier reef shelf australia abstract the application of sequence stratigraphic analysis to post glacial sediments requires the correct identification of sequence boundaries flooding surfaces and systems tracts the nature of coastal sediments deposited during sea level cycles is complex and misinterpretation is easy particularly in ancient sequences for which eustasy is inferred rather than demonstrated a large core seismic and radiocarbon database from cleveland bay in tropical queensland allows detailed analysis of the systems tracts and parasequences developed during the late holocene despite the large database a unique sequence stratigraphic interpretation is not possible because oscillations in the sea level curve apparently occurred at a frequency higher than the resolving power of radiocarbon dating our best estimate is that the final stages of the holocene sea level rise comprise four parasequences each deposited during episodic slowdowns in sea level rise and or a pulse of rapid sediment supply sea level pauses probably occurred at 12 10 m below modern levels at 8 5 ka bp followed by a fall to ca 17 m at 8 1 ka bp a very rapid transgression to ca 10 m at 7 9 ka bp a further transgression to ca 5 m at 6 8 ka bp and a final rise to the holocene highstand at 1 65 m at 5 5 ka bp the stratigraphic record of these sea level rises is complex occurs within the modern shore connected sedimentary wedge and comprises parasequences associated with shorelines at 11 m p11 17 m p17 10 m p10 5 m p5 and 1 65 m p 1 7 each parasequence comprises in ascending order onlapping estuarine shoreline sediment including mangrove mud and beach sand and progradational shallow bay muddy sand across the bay units up to and including the lower parts of the shallow bay mud correspond to the transgressive systems tract tst of the last 18 ka glacial interglacial cycle the particular parasequence represented being dependent upon location especially depth bay mud above this level corresponds to the post 5 5 ka bp highstand systems tract hst which comprises sand cheniers on the coastal plain and bioturbated muddy sand in the shallow bay the junction between the tst and the hst lies within the bay mud and corresponds approximately to the local flooding surface for the p 1 7 parasequence deposited at the 1 65 m shoreline offshore terrigenous tst strata do not occur over most of the middle and outer shelf which instead is veneered with a thin mid cycle shellbed the lower part of this shellbed is time equivalent to the later part of the tst and the upper part is time equivalent to the hst offshore the maximum flooding horizon mfh and peak eustatic sea level horizon pesh of the late pleistocene holocene sea level cycle lie at some level within the mid cycle shellbed nearshore the mfh and pesh lie within the shore connected sediment wedge at levels near the tst hst boundary however at no locality do either the mfh and pesh necessarily correspond to a physical boundary within the stratigraphy

fingerprints and age models for widespread new zealand tephra marker beds erupted since 30 000 years ago a framework for nz intimate abstract the role of tephras in the nz intimate project is a critical one because most high resolution palaeoclimatic records are linked and dated by one or more tephra layers in this review first we document eruptive distributional and compositional fingerprinting data both mineralogical and geochemical for 22 key marker tephras erupted since 30 000 years ago to facilitate their identification and correlation we include new glass compositional data the selected marker tephras comprise 10 from taupo and nine from okataina volcanoes rhyolitic one from tuhua volcano peralkaline rhyolitic and one each from tongariro and egmont volcanoes andesitic second we use four approaches to develop 2 age models for the tephras youngest to oldest 1 calendar ages for kaharoa and taupo y were obtained by wiggle matching log derived tree ring sequences dated by 14c 2 whakaipo v was dated using an age depth model from peat 3 14 tephras in the montane kaipo peat sequence waimihia s unit k whakatane tuhua mamaku rotoma opepe e poronui c karapiti b okupata konini waiohau rotorua rerewhakaaitu were dated by simultaneously wiggle matching stratigraphic position and 51 independent 14c age points against intcal04 using bayesian probability methods via both oxcal and bpeat and 4 the five oldest tephras erupted before ca 18 000 cal yr bp were dated by calibrating limited numbers of 14c ages using intcal04 okareka or comparison curves of the expanded cariaco basin sequence te rere kawakawa oruanui poihipi okaia kawakawa oruanui tephra the most widely distributed marker tephra was erupted probably ca 27 097 957 cal yr bp potential dating approaches for the older tephras include their identification in antarctic ice cores if present or annually laminated sediments for which robust calendar age models have been constructed high precision ams 14c dating on appropriate material from environmentally stable sites systematic luminescence dating or new radiometric techniques e g u th he if suitable minerals are available and errors markedly reduced further application of bayesian age modelling to stratigraphic sequences of 14c ages possibly augmented with luminescence ages may help refine age models for pre holocene tephras with the largest errors finally we discuss the critical role these marker tephras play in the ongoing construction of an event stratigraphy for the new zealand region which is a key objective of australasian and southern hemisphere intimate projects

holocene development of an episodic transgressive dune barrier ramsay bay north queensland australia abstract an investigation of the stratigraphy and sedimentological properties of a tombolo barrier at ramsay bay north queensland has indicated that the barrier consists largely of aeolian sands which in places extend more than 30 m below present sea level two major episodes of dune activity are recognized on morphological and pedogenic criteria radiocarbon dating of organic muds associated with the barrier sands suggests the older dunes were partly drowned during the early holocene marine transgression 9500 6000 c 14 yrs b p the later generation of dunes formed in the late holocene probably within the last 900 c 14 yrs the ultimate causes of the aeolian episodes are not certain but appear to be related to periods of rapid shoreface erosion

positive relief over buried post glacial channels great barrier reef province australia abstract continuous seismic profiling on the continental shelf central great barrier reef province australia has delineated a major sub bottom reflector interpreted as the pre holocene surface channels eroded in this surface are infilled and overfilled by post glacial sediments filling is ascribed to estuarine backfilling during sea level rise followed by deposition of delta front deposits in many cases these fills create positive relief over buried channels hence modern shelf morphology may not be an accurate guide to the positions of pleistocene channels across the shelf

natural deformation and recrystallization of some intermediate plagioclase feldspars abstract intermediate an25 an48 plagioclase feldspars from the nordre stromfjord shear zone central west greenland have undergone extensive ductile deformation by intracrystalline slip and by twinning the plagioclases were deformed under low granulite facies conditions optical substructures include undulatory extinction deformation bands subgrains and deformational twins mainly on the albite law dynamic recrystallization occurred primarily by subgrain rotation with bulge nucleation migration of a high angle boundary as a secondary mechanism in some cases recrystallization is accompanied by a small decrease in the an content which is thought to indicate prograde metamorphic conditions the plagioclases exhibit a good crystallographic preferred orientation which is compatible with 010 001 being the principal slip system quartz has in the same rocks undergone more plastic deformation and more extensive recovery than plagioclase this is at least in part due to the fact that most dislocations in plagioclase are dissociated

faulting and extension rate over the last 20 000 years in the offshore whakatane graben new zealand continental shelf oblique rifting in the offshore taupo volcanic zone new zealand is expressed in widely distributed active normal faulting in the 20 km wide whakatane graben active faults are identified along seafloor scarps and displacements of the post last glacial transgressive ravinement surface 400 faults we derive an extension rate at seismogenic depths 6 10 km across the graben of 13 6 mm yr by summing surface measurements assuming an average crustal fault dip of 45 15o and correcting for the discrepancies between surface and deep crustal extension estimates structural and kinematic data implies an extension direction 20o oblique to the rift axis resulting in up to 4 6 2 1 mm yr of dextral motion parallel to the rift axis the strike slip motion is accommodated by dip slip displacements on oblique faults in the centre of the graben and oblique slip faulting along the rift margins pure dip slip in the graben centre represents 50 of the total slip with the rangitaiki fault accommodating 25 of the total extension in the graben

chronology of palaeoclimatic change at the end of the last glaciation analysis of sediments recorded in a piston core located east of southern north island new zealand gives a detailed record of climate change at the end of the last glacial accumulation rates1 of both detrital quartz and biological carbonate and biogenic silica components of the sediment are much higher during glacial than post glacial time and they all show a synchronous rapid decline at 14 700 yr bp we attribute this to a decline in intensity of the strong glacial westerly winds in the new zealand region as the polar winds contracted to their present latitudes2 6 the greatest rate of quartz accumulation occurs between 16 200 and 14 700 yr bp and is not matched by any change in carbonate or silica accumulation we believe this reflects accelerated fluvial transport of detritus out of the mountain ranges and consequently increased aeolian dust transport before the decline of the polar westerlies

rock mass strength and slope stability of the hilina slump kīlauea volcano hawai i abstract stability of the hilina slump on the south flank of k lauea volcano hawai i is investigated using slope stability analyses based on rock mass mechanics the hilina slump is an active example of the giant landslides that are observed around submarine flanks of ocean island volcanoes based on edifice topology along with derived rock mass strength and deformability parameters slope stability analyses predict that the geometries of present day failure surfaces of the hilina slump are shallow located at less than 3 5 km depth below the upper surface of the edifice the failure surfaces at the base of the hilina slump are predicted to be structurally independent from a previously interpreted subjacent detachment at the contact between the k lauea edifice and the oceanic crust based on these model results the hilina slump is envisioned to ride atop the south flank of k lauea as it spreads seaward along this slipping basal detachment under present day slope and sea level configurations local horizontal ground accelerations greater than 0 4 0 6 g are predicted to cause slip along failure surfaces within hilina slump therefore dynamic stress changes due to slip along the subjacent detachment may potentially trigger slip along failure surfaces of the hilina slump model derived stability and failure surface geometries can account for the distinct observed distribution of slip along specific hilina faults following the m fa 7 9 1868 ka u and m s 7 2 1974 kalapana earthquakes further the spatial distribution of south flank aftershocks m 1 5 recorded between 1950 and 1976 are consistent with the predicted distribution of potential earthquake induced slip of the hilina faults

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

review of the chronology of marine terraces in the hawaiian archipelago abstract this chronology of marine terraces in hawaii includes 236 published dates most samples are from the emerged reef terraces on oahu the holocene record of transgression is outlined by the available data but further detailed work is needed a mid holocene high stand has been documented for kauai and is currently being resolved for oahu a double marine transgression during the last interglacial is suggested by stratigraphy and electron spin resonance dates from a newly studies site on oahu precise radiometric dates are needed to confirm this interpretation attention is called to the emerged terraces above 10 m in the hawaiian islands which initial studies indicate are older than the last interglacial a reevaluation of oahu age data suggests that oahu has undergone uplift during the last 500 000 years and may not be a suitable stable platform for eustatic sea level comparisons a promising set of deeply submerged terraces representing eustatic low stands has been discovered off the island of hawaii these drowned reefs offer potential for paleoceanographic and paleoclimatic studies

submerged shoreline preservation and ravinement during rapid postglacial sea level rise and subsequent slowstand submerged shorelines hold much potential for examining the interplay between the rate of sea level rise and geomorphic setting and informing the development of models of contemporary shoreline behavior this paper describes the sedimentary architecture of a submerged barrier shoreline complex off durban south africa the complex consists of several barriers that have survived the postglacial transgression and associated erosive ravinement processes the main shoreline sequence 60 m dates to 11 690 90 calibrated cal yr b p and rests on a pleistocene lagoonal deposit 35 395 592 cal yr b p the entire barrier shoreline complex is truncated by a strongly diachronous wave ravinement surface the ravinement surface seaward of the main 60 m shoreline is steep but the gradient declines across and landward of the subordinate landward shoreline complexes the steep ravinement surface is attributed to fast sea level rise possibly associated with meltwater pulse 1b while the gentle ravinement surface is associated with a subsequent slowing of the rate of sea level rise to 0 15 mm yr 1 preservation of the main barrier and back barrier deposits through overstepping is associated namely with rapid transgression and increased back barrier accommodation the smaller barriers landward of the main barrier were preserved through overstepping related to gentle antecedent gradients despite more intense ravinement during a very slow rise in sea level slowstand this process was assisted by a sediment deficit the resulting post transgressive drape is also influenced by antecedent topography created by the barriers themselves damming along the landward sides of overstepped barriers thickens the drape and creates a temporal disconnect between the migration of the shoreface and more landward elements of the littoral system in examining the rates of shoreline migration associated with the overstepped barrier system these are far greater than those calculated for the predicted rates of shoreline change on similarly steep coastal profiles future rates of shoreline migration appear to be insufficient to cause overstepping and rollover or erosional responses are more likely

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

inner forearc sequence architecture in response to climatic and tectonic forcing since 150 ka hawke s bay new zealand the influence of eustasy tectonic deformation and sediment flux as controlling parameters on basin stratigraphy and depositional sequence development are largely accepted eustasy is usually considered as the dominant mechanism of sequence generation especially for pleistocene successions in active subduction margin settings the high rates of tectonic deformation are expected to have a stronger influence on basin fill architecture while sediment flux is generally less well constrained and therefore less frequently considered the active hikurangi subduction margin in new zealand offers the opportunity to quantitatively assess the relative roles of tectonic climatic and eustatic drivers we present a quantitative source to sink like study of the late pleistocene succession from the hawke s bay sector of the inner forearc domain c 150 ka to present the interpretation of a grid of high resolution marine seismic data onland and offshore core and well descriptions and the integration of geomorphic studies enabled identification of system tracts in turn these comprise two sea level cycle depositional sequences lps1 and lps2 including one complete 100 ka sequence lps1 isopach maps of both sequences reveal changes in sediment distribution and preservation that reflect the relative roles of tectonic deformation and eustasy eustasy dominates development of sequence architecture at relatively short time scales i e 100 kyrs four long lasting depocenters are identified over the inner forearc domain and located in four subsiding basins kidnappers mahia lachlan and motu o kura basins significant shifts of the depocenter location in the basins are correlated with eustatic sea level changes estimates of sediment volumes and masses from isopach maps indicate higher mass accumulation rates during climato eustatic extremes which we correlated to the onland erosional response sediment distribution and landscape evolution are strongly influenced by the interaction of the structural deformation and sediment flux we present paleogeographic reconstructions for the inner forearc domain coincident with two paleoclimatic extremes last glacial maximum and holocene optimum these illustrate the importance of eustatic changes structural deformation and sediment flux on the pattern of sediment distribution accumulation and sequence architecture

submergent shorelines in the sw pacific evidence for an episodic post glacial transgression high resolution seismic profiles supported where possible by radiocarbon dates and regional stratigraphic data indicate that the last post glacial transgression in the sw pacific was episodic comprising major stillstands punctuated by rapid rises in sea level on the terrigenous continental shelf east of south island new zealand a succession of shorelines s8 s1 are recognized as follows s8 c 113 m 18 000 yr bp s7 c 88 m 17 000 yr bp s6 c 75 m 15 000 yr bp s5 c 56 m 12 000 yr bp s4 c 46 m 11 000 yr bp s3 c 28 m 9 500 yr bp s3a c 24 m 9 000yr bp s2 c 9 m 7 500yr s1 0 m 6 500yr bp with the exception of s8 and possibly s2 the shorelines are associated with wedges of sediment the size and presence of which imply that 1 sea level stabilized at some shorelines for a considerable period of time up to i 2 000 yr and 2 the intervening rises of sea level estimated to have been at least 10 12 m lo3 yr were too rapid to allow the reworking of the wedges into a transgressive sediment sheet as favoured in some current models on the great barrier reef shelf off queensland australia shorelines s8 sl have also been recognized with a further shoreline feature s4a occurring at c 39 m shorelines sla 0 m o yr bp slb 2 3 m 6 000 yr bp and slc 0 m 6 500 yr bp are recognized as discrete aspects of the post 6 500 yr bp sea level behaviour in north eastern australia the rapid rise in sea level at least between shorelines s5 12 000 yr bp and 53 9 500 yr bp is known to have outpaced reef growth causing in situ drowning of reefs located along the deeper shorelines all modern reefs so far drilled and dated began their development at or above s3 28 m 9 500 yr bp some of the shorelines particularly s5 appear to correlate between the northern and southern hemispheres on the basis of age succession and general depth of occurrence suggesting 1 that they may be global features controlled by the post glacial pattern of ice sheet decay and 2 that hydro isostatic adjustment may exert only a minor control on the depth of particular shorelines at least during the earlieg parts of the post glacial transgression

current modification of a mass failure deposit on the continental shelf north canterbury new zealand abstract the holocene mud blanket on the nearly flat 0 4 middle to outer shelf off canterbury contains a 255 km 2 zone of ridges and gullies exhibiting up to 10 m relief ridges are mantled by cohesive mud in various stages of dissection whereas gullies mainly have a flat sandy floor morphologic and seismic evidence suggests that the topography initially formed by mass failure along an unconsolidated sand horizon which presumably acted as a failure plane a number of mechanisms are readily available to favour such movement earthquake shock sediment overloading subsurface instability due to gas and wave loading since formation the topography has been modified by currents which have eroded mud from gullies as well as locally scouring ridge crests current meter measurements from 1 m above a ridge crest indicate that erosion most likely occurs under storm conditions when currents reach a laboratory determined threshold speed of 100 37 cm s 1 in contrast undissected crests may be resistant to erosion as a consequence of biological stabilization by dense colonies of chaetopterid worm tubes or associated biota

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

internal structure and evolution of the late quaternary sequence in a shallow embayment the amvrakikos gulf nw greece abstract the late quaternary stratigraphic pattern of the amvrakikos gulf in the eastern mediterranean has been studied on the basis of the analysis of high resolution seismic profiles and short sediment cores lowstand transgressive and highstand systems tracts have been identified that are configured in a major depositional sequence of a fifth order sea level cycle during the last glaciation when the sea level was lowered by 55 m relative to its present position ca 50 ka bp the amvrakikos gulf was probably emerged giving rise to a subaerial erosion and fluvial incision in the western shallow part of the gulf and b development of a paleo lake in the eastern deepest domain until the early phase of the post glacial transgression ca 11 50 ka bp a paleo river characterized by a dense network of v shaped valleys was draining the western part of the gulf and flowing into the ionian sea in the isolated eastern part lowstand lacustrine deposits deltaic and prodeltaic units accumulated within the paleo lake at the latter stage of the last post glacial transgression ca 11 ka bp seawater entered the gulf and the transgressive systems tract was deposited consisting of incised channel fills beach shoreface deposits and delta prodelta wedges buried terraces have been identified also within this transgressive tract that reveal a step like sea level rise since ca 6 ka bp when the sea level reached its present day position a distal prodeltaic unit has been deposited and overlain by prograding deltaic wedges the spatial distribution of these wedges provides evidence of a continuous shifting of the river mouths during holocene the recent sedimentation patterns are related to the terrigenous inputs primarily from the arachthos river located in the northeastern part of the gulf and secondarily from the louros river located in the northwestern part

geomorphology of submerged reefs on the shelf edge of the great barrier reef the influence of oscillating pleistocene sea levels the submerged reefs on continental margins and surrounding oceanic islands are important archives of past climates eustatic sea level oscillations and oceanographic processes australia s north eastern submerged shelf edge reefs have previously been explored but all studies have been limited by either low resolution single beam profiles or by their limited spatial extent the aim of this study is to improve the understanding of the origin and development of submerged shelf edge reefs terraces and related features on the great barrier reef gbr and the influence of pleistocene sea level oscillations on their distribution and geomorphology we investigated the first large scale 1400 km2 3d bathymetry and acoustic backscatter dataset of four widely spaced sites located across ca 650 km along the shelf edge at ribbon reefs 1 5 noggin pass viper reef and hydrographers passage we provide a comprehensive description and systematic classification of the shelf edge features and constrain their spatial distribution and geomorphologic variability using a wide range of quantitative morphometrics fifteen features are defined four of which are the focus of this study including terraces pinnacles ridges and channels using modern reefs within the gbr for comparison we interpret these as fringing reefs patch and barrier reefs and tidal channels respectively the influence of gross shelf geomorphology and oceanographic factors driving the observed variability within and between sites is discussed in conjunction with mid late pleistocene sea level oscillations we observed two distinct types of reef growth characterised by the degree of development which we interpret as analogous to juvenile and mature modern reefs of the gbr juvenile reefs are very common and occur within each site at depths of less than 50 m to greater than 100 m they are defined as discontinuous peaked barrier reefs peaked patch reefs and fringing reefs mature reefs are less common and develop exclusively at a depth range of ca 50 70 m these reefs are defined as flat topped continuous barrier and double barrier reefs through a comparison with published mid late pleistocene sea level oscillations we note that the depth range of mature reefs is consistent with the depth of repeated low amplitude 20 m eustatic sea level oscillations and independent of the relative time spent at sea level we conclude that repeated low amplitude sea level rises provide the much needed accommodation space for vertical accretion that is not provided during stillstands without inducing reef drowning which can be caused by high amplitude sea level rise low amplitude sea level falls are also less detrimental than high amplitude falls in terms of habitat compression together the effects of enhanced reef accretion and limited habitat compression at depths of 50 70 m have lead to a concentrated net gain in vertical relief that is not observed elsewhere on the shelf edge

epeirogenic plate movements consideration is given to the kinematics of epeirogenic movements over the recent geologic past late pleistocene in a region for which there is an abundance of geological and geophysical information the continental shelf off the east coast of north america it is found that there has been a relative change in elevation of 140 m downward toward the northeast over this longitudinal distance of 3000 km during the past 18 000 years specifically miami has been elevated at a rate of 0 8 cm yr with respect to the scotian shelf continental margin the confirming data include the shelf break corrected for progradation reef building and glacio isostatic adjustment late pleistocene shores on the continental shelf earlier pleistocene unconformity surfaces dated geologic samples of known shallow water origin buried pleistocene channels and recent leveling analysis

normal fault growth and linkage in the whakatane graben new zealand during the last 1 3 myr determination of fault growth rates and fault network evolution at time scales from 104 106 years has been hampered by a lack of a well constrained stratigraphic succession that provides a high fidelity record of fault development over these time periods here we show how seismic reflection data of different spatial resolutions can be used to constrain the linkage history and displacement rate variations of a single major fault we present data collected in the offshore whakatane graben bay of plenty new zealand where intense normal faulting occurs as a result of active back extension the focus of our study is the rangitaiki fault a linked segmented normal fault which is the dominant active structure in the graben the total linked fault length is c 20 km long and has a displacement of up to 830 130 m in the top 1 5 km of sediments the fault has been actively growing for the last 1 34 0 51 ma and has developed from isolated fault segments to a fully linked fault system initially the dominant process of fault growth was tip propagation with an average and maximum displacement rates of 0 52 0 18 mm yr 1 and 0 72 0 23 mm yr 1 respectively interaction and linkage became more significant as the fault segments grew towards each other resulting in the fault network becoming fully linked between 300 and 18 ka following fault segment linkages the average displacement rate of the fault network increased by almost three fold to 1 41 0 31 mm yr 1 while the maximum displacement rate increased to 2 72 0 61 mm yr 1 this is the first time that the growth rate of unlinked fault segments has been resolved and has been shown to be slower than in the subsequent linked fault system

a drowned holocene barrier spit off cape ann massachusetts seismic profiles and bathymetric contours reveal a drowned barrier spit on jeffreys ledge off cape ann massachusetts seaward dipping internal reflectors indicate that a regressive barrier formed during the early holocene low sea level stillstand preservation of the barrier spit may have been favored by its large size as much as 20 m thick by an ample sediment supply from unconsolidated glacial drift and by the subsequent rapid sea level rise the barrier spit is present in water depths of 50 to 70 m and indicates a low relative sea level stand of 50 m this value confirms the low relative sea level stand of 47 m postulated by oldale et al 1983 for northeast massachusetts and new hampshire on the basis of the submerged delta of the merrimack river and it indicates that the barrier and delta were contemporaneous oldale et al 1983

holocene paleoseismic history of upper plate faults in the southern hikurangi subduction margin new zealand deduced from marine terrace records abstract the formation and uplift of holocene marine terraces along a 160 km long stretch of the wairarapa coast in the southern hikurangi subduction margin north island new zealand are interpreted in terms of causative faults and associated large earthquakes during the past circa 7000 cal yr b p distinctive stepped terrace morphology the clustering of radiocarbon ages on each uplifted terrace and the historic occurrence of coseismic uplift in other parts of eastern and southern north island support the contention that coastal uplift occurred suddenly and repeatedly during large magnitude earthquakes the rupture of five west dipping reverse or reverse oblique faults within the australian plate whose surface traces lie a short distance seaward of the present shoreline are inferred to be responsible for coastal uplift individual structures range in length from 25 to 60 km these lengths together with uplift events in the range of 1 4 m suggest earthquakes in the range of m w 7 7 5 approximately 20 of the radiocarbon ages are anomalously young for their elevations but many have ages indistinguishable from accepted ages for terrace uplift we infer that many of the anomalous ages are from samples deposited by tsunami that occurred in association with offshore fault rupture on adjacent sections of the coast

seismic imaging of the alpine fault near inchbonnie new zealand 1 the transpressive alpine fault is the boundary between the pacific and australian plates across the south island of new zealand earthquakes on the alpine fault and related structures pose a serious risk to many urban centers including the city of christchurch although it is a major feature on satellite images the alpine fault is a difficult target for surface studies along much of its length it mostly traverses densely forested and mountainous terrain and where it occurs in the lowlands it is usually covered by recent sediments to investigate the alpine fault at a rare accessible location inchbonnie we have acquired high resolution seismic reflection data along five 380 1200 m long lines images produced from these data reveal a glacially overdeepened valley containing a thick sequence of diverse glacigenic sediments that have been disrupted by three en echelon strands of the principal alpine fault and several secondary fault strands based on their seismic facies the sedimentary sequence is interpreted to comprise basal lacustrine beds overlain successively by alluvial colluvial deposits that possibly include the remnants of large landslides deltaic fan units and braided river gravels whereas the principal alpine fault strands disrupt the entire post glacial sedimentary section and likely offset basement at depths up to 400 m most of the secondary faults either merge with the principal fault strands at shallow depths or are surficial features limited to the sedimentary section

deformation of granitic rocks across the brittle ductile transition abstract a microstructural analysis has been carried out on mylonites and mylonitic gneisses of the eastern peninsular ranges mylonite zone which were formed over a range of metamorphic conditions from lower greenschist to amphibolite facies composite planar fabrics in the form of c and s planes are found at all metamorphic grades fractured feldspars kinked biotites and ductile deformation of quartz characterize the lower greenschist facies mylonites at mid upper greenschist grade orthoclase grains show dynamic recrystallization textures whereas plagioclase exhibits low temperature plasticity with only minor recovery biotite ribbons form by progressive rotation and coalescence of kink band segments to produce chevron fold patterns at epidote amphibolite grade and above recovery processes and annealing recrystallization predominate in all minerals residual orthoclase porphyroclasts show strain related myrmekite formation along those sides of the grains that face the instantaneous shortening direction myrmekite formation due to replacement reactions cannot explain this geometry it is proposed that the myrmekites formed due to a combination of exsolution replacement and strain enhanced diffusion

across shelf sediment dispersal hauraki gulf new zealand abstract side scan seismic and surficial sediment data accompanied by current meter records highlight across shelf sediment transport in hauraki gulf an island studded embayment off northern new zealand calm weather currents are locally dominated by the tides with periodic incursions of oceanic water from detached meanders of the east auckland current under these conditions bedload transport occurs mainly in three 15 20 km wide channels where bathymetric intensification of the flow brings about near bottom speeds of up to 82 cm s 1 for colville channel and 33 44 cm s 1 in jellicoe and cradock channels surficial sediments are gravelly to muddy sand winnowed in places leaving a lag deposit of mainly biogenic carbonate gravel modelling results suggest that in colville channel dominant fine to medium sand modes are mobile for 20 60 of the time with a net eastward movement for fine sand in jellicoe and cradock channels the prevailing direction of transport is southwards across the shelf with sand mobile for up to 33 of the time oceanic incursions have the potential to boost flow in the western gulf however such incursions are transitory and there is no measurable expression of oceanic water in the sedimentary record because of their association with prolonged periods of calm weather the incursions are unlikely to accompany storm events where their cumulative effect might be important for sediment transport near bottom currents resulting from oceanic incursion may reinforce peak tides inside the gulf by up to 2 4 cm s 1 enhancement of prevailing water motions occurs during periods of extreme weather during cyclone drena january 1997 measured flow speeds in jellicoe channel reached 48 cm s 1 furthermore the disturbance generated large waves that stirred bottom sediments down to over 100 m water depth such events are probably the major agent of sediment redistribution in the hauraki gulf the net effect of storm and calm weather currents is to move sediment across the outer to middle shelf where in the western and central gulf it accumulates and in the eastern gulf it escapes eastward via colville channel

environmental and sea level changes on banks peninsula canterbury new zealand through three glaciation interglaciation cycles abstract a greater than 200 ka record of marine transgressions and regressions is recorded from a 75 m core from banks peninsula canterbury new zealand this record comprises thick suites of muddy sediments attributed to back barrier lake and lagoonal environments alternating with thin soil and loess complexes these deposits have been dated using radiocarbon and thermoluminescence tl techniques supported by proxy data diatoms phytoliths pollen and sedimentology the aqueous deposits are attributed to three interglacials and an interstadial marine isotope stages 1 5a 5c 6 and 7 the loesses and paleosols date to the intervening stadials isotope stages 2 5d or 6 and probably 8 on the basis of transgressive beach facies back barrier swamps and barrier blocked lake deposits a partial sea level curve including data from isotope stage 5 is presented our data indicate that banks peninsula has been tectonically stable over that period and we provide sea level points that support the existing isotope curve during stages 5 and 6 detailed diatom records are limited to isotope stage 1 and the latter part of stage 5 diatom histories recorded from these stages are remarkably consistent both indicate a progressive floral change from marine types through freshwater colonising species to freshwater planktonic assemblages these reflect parallel histories of coastal evolution during the two interglacials in both cases marine transgression in the early part of the isotope phase was followed by lagoon development implying that a gravel spit extended across the embayment from the west this was succeeded by lake development when the lagoon was cut off by the juncture of the spit with banks peninsula this lake deepened as the coast rotated into swash alignment and the spit was converted into a gravel barrier the vegetation history of the site indicates that mixed podocarp broadleaf forests similar to the pre european flora of banks peninsula occupied the region during isotope stages 1 and 7 this contrasts with the palynological interpretation of a marine record dsdp site 594 from off the canterbury coast which suggested that isotope stage 7 was markedly cooler than the holocene during glacial periods forest was eliminated and replaced by a tall shrubland of mixed montane and coastal affinities

early holocene paleoseismic history at the pakarae locality eastern north island new zealand inferred from transgressive marine sequence architecture 1 early holocene transgressive marine deposits infilling the pakarae river paleovalley are used to extend the paleoseismic history of the pakarae river locality east coast north island new zealand back in time prior to eustatic sea level stabilization at 7 calibrated cal ka b p paleoenvironmental evolution of the pakarae river paleovalley from 7 to 10 cal ka b p is reconstructed using sedimentology and biostratigraphy two estuarine units display sudden vertical transitions to floodplain sediments implying significant marine regressions and estuary abandonment these regressions are attributed to coseismic coastal uplift events at 9000 and 8500 cal years b p a third uplift between 8500 and 7350 cal years b p is inferred from a significant difference between the amount of sediment preserved and the predicted sediment thickness according to the eustatic sea level curve this study demonstrates the utility of the analysis of transgressive deposits and their paleoenvironmental characteristics for neotectonic investigations on active coasts

high resolution record of displacement accumulation on an active normal fault implications for models of slip accumulation during repeated earthquakes the spatial and temporal accumulation of slip from multiple earthquake cycles on active faults is poorly understood here we describe a methodology that can determine the time period of observation necessary to reliably constrain fault behaviour using a high resolution longtimescale the last 17 kyr fault displacement dataset over the rangitaiki fault whakatane graben new zealand the fault linked at ca 300 ka bp and analysis of time periods within the last 17 kyr gives insight into steady state behaviour for time intervals as short as ca 2 kyr the maximum displacement rate observed on the rangitaiki fault is 3 6g1 1 mm yr k1 measured over 17 kyr displacement profiles of the last 9 ka of fault movement are similar to profiles showing the last 300 ka offault movement in contrast profiles determined for short time intervals 2 3 kyr are highly irregular and show points of zero displacement on the larger segments this indicates temporal and spatial variability in incremental displacement associated with surface rupturing slip events there is spatial variability in slip rates along fault segments with minima at locations of fault interaction or where fault linkage has occurred in the past this evidence suggests that some earthquakes appear to have been confined to specific segments whereas larger composite ruptures have involved the entire fault the short term variability in fault behaviour suggests that fault activity rates inferred from geodetic surveys or surface ruptures from a single earthquake may not adequately represent the longer term activity nor reflect its future behaviour different magnitude events may occur along the same fault segment with asperities preventing whole segment rupture for smaller magnitude events q 2006 elsevier ltd all rights reserved

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

timing of deglaciation from an oxygen isotope curve for atlantic deep sea sediments the exact timing of deglaciation is an important issue in the context of climatic feedback involving the deglacial rise in atmospheric co2 seen in ice cores1 4 we have produced evidence from box cores taken in the equatorial atlantic that the last deglaciation occurred in two major steps which were separated by a brief pause5 here we propose that this pause is equivalent to the period of glacial readvance known as younger dryas which lasted from about 11 to 10 kyr bp if our correlation is correct then the initiation of deglaciation occurred after 14 kyr bp which disagrees with most other deep sea timescales

sedimentation in the conway trough a deep near shore marine basin at the junction of the alpine transform and hikurangi subduction plate boundary new zealand the conway trough is a 40 km 10 km 1000 m deep rectangular tectonically controlled sedimentary basin situated on an active plate boundary the basin lies at the junction of the alpine transform and hikurangi subduction sectors of the indo australian pacific plate boundary it is incised into cainozoic sedimentary rocks and contains a thick fill of late neogene sediment study of the continental shelf near the conway trough indicates 1 that transport mechanisms operate in a net north easterly direction and 2 that the neritic sediment drift system is confined to within a few kilometres of the shoreface with the result that 3 large areas of the shelf south of the trough comprise bare bedrock or relict late pleistocene sediment despite reaching to within 3 km of shore the conway trough receives little modern bedload sediment as indicated by a paucity of sand fill however the trough has intercepted some holocene bedload since the main channel contains redeposited graded gravel and sand with a c 14 age of 4670 yr satellite imagery and piston cores reveal that abundant mud is provided to the trough much of it from river sources up to 200 km to the south some of this sediment is inferred to move by turbid layer transport through conway trough and out via kaikoura canyon into nearby hikurangi trough nonetheless sedimentation rates in the conway trough may be as high as 1 7 m 1000 yr 1 the conway trough forms a modern example of a transform basin varying neogene examples of which are found widely in north eastern south island sedimentation models are constructed to compare transform and transduction basins particularly with respect to the effects of pleistocene sea level changes

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

non tropical carbonate deposits on the modern new zealand shelf abstract extensive ca 50 000 km 2 shallow marine platforms 70 caco 3 despite proximity to a tectonically active plate margin in these regions the terrigenous sediment supply is presently low and growth of epibenthos is fostered by firm substrates rock gravels shells seaweeds and the generally energetic nature and high nutrient levels of open shelf waters rapid transition into adjacent terrigenous dominated facies is characteristic irrespective of water depth the carbonates are coarse grained and fragmental carbonate mud is rare calcite dominates over aragonite high mg calcite widespread off northern new zealand is rare in the south skeletal material is dominated by bryozoans and bivalve molluscs with significant local contributions from foraminifers barnacles calcareous red algae and echinoderms the name bryomol is suggested for this distinctive temperate region skeletal carbonate facies which can be usefully subdivided based on dominant zoarial growth forms of the bryozoan component known to be habitat related bioerosion is an important mechanism of skeletal fragmentation and degradation many grains especially aragontic bivalves are infested by endolithic borers and have low preservation potential ages of skeletal material in the surficial deposits range from more than 20 000 years b p to modern which is consistent with both low rates of carbonate production and sediment accumulation and the wide range in preservation state of grains some data suggest that the skeletal carbonates are dispersed and mixed mainly during infrequent movement of sand ribbons sand waves and sand sheets driven by storm assisted tidal flows tracts of modern palimpsest and relict carbonates can occur in juxtaposition the facies characteristics of the new zealand shelf carbonate deposits contrast significantly with those of the classical bahaman type carbonate model however they are similar to those reported from many other mid to high latitude carbonate shelves and afford good analogues for most onland occurrences of new zealand cenozoic limestones

cliff overstep model and variability in the geometry of transgressive erosional surfaces in high gradient shelves the case of the ionian calabrian margin southern italy abstract chirp subbottom profiles performed on the ionian calabrian margin southern italy allow the recognition of an irregular step like seabed topography and a marked variability in the geometry of the post last glacial maximum lgm transgressive wave ravinement surface wrs the wrs truncates an older unit showing locally an opaque seismic character and displays both concave up and concave down profiles in any dip section and a local stepped geometry with gradients between 1 and 20 a younger unit characterized by high amplitude reflectors onlapping or draping the wrs is interpreted as a sediment wedge accumulated during the post lgm glacio eustatic rise the wrs crops out forming steep slopes up to 12 which are interpreted as relicts of palaeo coastal cliffs generated by wave action during relative sea level rise in particular the deeper slope is locally exposed between ca 75 and 100 m water depth corresponding closely with the depth range of melt water pulse mwp 1a 14 3 14 0 ka bp assuming no subsidence or uplift and its generation is inferred to be related to this event a transgressive model for high gradient settings and stepped sea level rise is proposed coastal cliffs develop and retreat due to wave erosion during phases of slow relative sea level rise during phases of very high rate of relative sea level rise coinciding with melt water pulses cliffs tend to be overstepped drowned and not completely eroded by the wrs such a cliff overstep transgressive model is the equivalent in high gradient settings of the in place drowning model developed for low gradient shelves the present model may be effective in reconstructing stepped sea level rises and the evolution of shelf areas during late quaternary time

geomorphic and stratigraphic signals of postglacial meltwater pulses on continental shelves selective development and preservation of major shoreline complexes on the continental shelf provide geomorphic evidence in support of alternating periods of holocene sea level stillstand and rapid rise during meltwater pulses on a tectonically stable far fi eld setting the southeast african shelf regionally developed well preserved shoreline complexes occur at 100 m and 60 m within an overall shelf sequence dominated by transgressive ravinement non preservation of shorelines the development of geomorphically mature submerged shorelines with equilibrium forms is attributed to extended periods of sea level stability and their preservation is the result of early cementation followed by very rapid sea level rise several centimeters per year that caused overstepping meltwater pulses 1a and 1b are recorded in the shelf stratigraphy and geomorphology setting aside local infl uences of topography and sediment supply we hypothesize that shelf stratigraphies should preferentially preserve shorelines at water depths associated with the stillstands or slowstands immediately preceding meltwater pulses a reappraisal of shelf stratigraphy and geomorphology in particular the preservation potential of former shorelines is required in the light of contemporary understanding of postglacial sea level history

1300 km long late pleistocene holocene shelf edge barrier reef system along the western continental shelf of india occurrence and significance abstract a detailed analysis of echosounding and side scan sonar data collected from the western continental margin of india has revealed the presence of prominent shelf edge reefs concentrated mostly on the central and the southern parts their depth of occurrence varies between 85 and 136 m the reefs are 1 12 m high and 0 1 2 6 km wide av 700 m morphologically they may be classified into 1 simple and 2 complex types the former are single and broad or narrow av width 350 m while the latter are generally massive av width 950 m with several superimposed peaks sub bottom profiles indicate the presence of paleolagoons this reef system more than 1000 km long trends nnw sse i e parallel to subparallel to the present day shoreline it is surmised that coral algal reef growth commenced with the advent of the holocene transgression and favorable antecedent topography and continued until early holocene subsequently rapid sea level rise drowned the reefs the shelf edge reefs therefore are part of relict submerged barrier reef system and reflect late pleistocene early holocene shoreline

an examination of spatial variability in the timing and magnitude of holocene relative sea level changes in the new zealand archipelago holocene relative sea level rsl changes have been reconstructed for four regions within the new zealand archipelago the northern north island including northland auckland and the coromandel peninsula the southwest coast of the north island the canterbury coast south island and the otago coast south island in the north island the rsl highstand commenced c 8100 7240 cal yr bp when present mean sea level pmsl was first attained this is c 600 1400 years earlier than has been previously indicated for the new zealand region as a whole and is consistent with recent holocene rsl reconstructions from australia in north island locations the early holocene sea level highstand was quite pronounced with rsl up to 2 75 m higher than present in the south island the onset of highstand conditions was later with the first attainment of pmsl being between 7000 6400 cal yr bp in the mid holocene the northern north island experienced the largest sea level highstand with rsl up to 3 00 m higher than present this is demonstrably higher than the highstand recorded for the southwest north island and otago regions a number of different drivers operating at a range of scales may be responsible for the spatial and temporal variation in the timing and magnitude of rsl changes within the new zealand archipelago one possible mechanism is the north south gradient in rsl that would arise in the intermediate field around antarctica in response to the reduced gravitational attraction of the antarctic ice sheet ais as it lost mass during the holocene this gradient would be enhanced by the predicted deformation of the lithosphere in the intermediate field of the southern ocean around antarctica due to hydro isostatic loading and mass loss of the ais however no such long wavelength signals in sea surface height or solid earth deformation are evident in glacial isostatic adjustment gia model predictions for the new zealand region while research from australia has suggested that north south variations in holocene rsl changes due to hydro isostatic influences are limited or non existent at the regional to local scale post glacial meltwater loading on the continental shelf around new zealand is predicted by gia modelling to have a significant effect on the timing and magnitude of rsl changes through the phenomenon of continental levering the spatial variation in continental levering is controlled by the configuration of the coast and the width of the adjacent continental shelf with continental levering providing a robust explanation for the observed spatial and temporal variations in rsl changes further research is required to characterise the regional and local effects of different tectonic regimes wave climates and sediment regimes these are potentially very significant drivers of rsl variability at the regional to local scale however the magnitude of their potential effects remains equivocal

lowstand terraces on tyrrhenian sea steep continental slopes abstract wave built terraces formed during sea level stillstands at depths lower than present are found along margins with fairly steep morphology and no to ill developed continental shelf for instance the margin of volcanic islands terraces deposits are up to 20 30 m thick and are flat topped with well defined edges they extend up to 1 km in dip section the deposits are composed of intrabasinal sediments mainly bioclastic sand and silt and are probably due to deposition below the storm wave base during large scale energy episodes two areas of the tyrrhenian sea have been analysed one in a volcanic context the pontine archipelago and the other in a highly active structural context the calabrian arch similar wave built terraces were found in both areas with a main terrace placed at a depth of 100 150 m which is thought to be wurmian older terraces are also present emplaced during the preceding lowstands in the late pleistocene a possible present day terrace is found at about 20 m depth in the pontine archipelago a mechanism of subsequent formation below wave base level and removal because of sea level lowering has been hypothesised during long lasting periods of late pleistocene sea level falls terraces are thus thought to preserve only at the minimum lowstand position and to remain relict on the slope during sea level rise and highstand the analysis of the distribution and depths of these terraces allows some neotectonic interpretation for example in the volcanic archipelago whose western sector has probably risen at an average rate of 2 5 mm yr over the last 20 000 years

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

long term deformation and fluid enhanced mass transport in a variscan peridotite shear zone in the ivrea zone northern italy a microtextural petrological and geochemical study of a reactivated shear zone the microtextural petrological and geochemical study of a ductile shear zone in the phlogopite peridotite of finero ivrea zone northern italy reveals the long term deformation of this zone the zone is divided into a protomylonitic and an ultramylonitic part both parts reflect different periods of deformation although the orientation of the mineral lineations does not change in the coarse grained part period 1 the deformation started under granulite facies conditions about 775 c olivine ortho and clinopyroxene and phlogopite recrystallized dynamically in the ultramylonitic part relics of the granulite facies event and evidence for a continuous or two stage deformation history under amphibolite facies minimum 640 c to upper greenschist facies conditions maximum 520 c are preserved period 2 amphibolite facies conditions are indicated by olivine recrystallization the monoclinization of orthopyroxene porphyroclasts and the recrystallization and chemical changes of clinopyroxene the greenschist facies final stage of period 2 is characterized by decreased x co 2 and the syntectonic formation of antigorite tremolite and phlogopite at the expense of recrystallized and porphyroclastic olivine and pyroxene between both deformation periods a short break in deformation continuity is probable continuous deformation or reactivation in shear zones of the ivrea zone has not been described so far during the granulite facies shearing small amounts of channelized fluid flow led to a slight mass transfer the shear zone shows a moderate enrichment of na ba cu cs h2o and co2 and a small loss of p the mass balance of the ultramylonite indicates a significant increase in mass transport a mass gain can be inferred for h na k ba al ti p s cs sr rb c zn zr s sc light rare earth elements nb cl and au the zone is depleted in ca cu co f and ni si mg cr mn y nb and v are constant within analytical error deformation and fluid infiltration led to a change in volume which increases during the granulite facies event by 5 7 and during the lower temperature phase by 3 3 the calculated fluid to rock ratios by standard equations results in unrealistically high values for the interpretation of highly deformed rocks with drastic grain size reduction it is therefore necessary to consider the enhanced diffusion which is mainly controlled by the increased grain boundary surface

holocene sea level curves for santa monica shelf california continental borderland a curve is constructed showing changes in sea level at the santa monica shelf over the past 18 000 years the curve is based on radiocarbon dates sedimentologic data and high resolution seismic stratigraphic analysis of late quaternary terrace deposits sea level was 117 meters below its present position about 18 000 years ago during the first 8000 years of the flandrian transgression sea level rose to at least 24 meters fell to about 46 meters and then rose to 20 meters all below present sea level subsequently sea level rose more slowly and without discernible interruption to its present position

deep crustal extensional faulting in the ivrea zone of northern italy abstract the ivrea zone in northern italy consists of amphibolite and granulite facies metasedimentary metabasic and ultrabasic rocks and is thought to represent a section through the deep continental crust detailed mapping of the high grade part of this zone has revealed a series of high temperature shear zones which after the effects of later low temperature faulting and folding have been removed appears to accommodate extension of the sequence the shear zones formed at temperatures similar to those at which thermal equilibration occurred in the host rocks and locally show evidence for development under prograde conditions these observations fit well with thermal effects calculated from a simple heat flow model for extensional faulting in this model the effects of shear heating and displacement of cool hanging wall rocks against hotter footwall rocks are calculated these observations indicate that faulting as a mode of failure may be important during extension of the lower continental crust especially when basic rocks are the dominant components of the rock pile a restored section through the extended lower crust as observed in the ivrea zone is presented and the extent to which the features observed are able to explain seismic reflectivity of the lower crust is discussed

the motunau fault and other structures at the southern edge of the australian pacific plate boundary offshore marlborough new zealand abstract the boundary between the indo australian and pacific plates passes through new zealand as the alpine fault then links northeastwards with the hikurangi subduction margin through the marlborough shear zone a group of five major subparallel transcurrent faults the southern limit of the marlborough shear zone is situated at the motunau fault a previously unrecognized offshore extension of the active porters pass fault and lineation system to the south of the motunau fault the kaikoura sequence cretaceous cainozoic sediments that underlie the canterbury continental shelf are effectively undeformed and lie outside of the plate boundary zone 3 5 khz profiler records and other marine geologic data collected on g r v tangaroa cruises 1097 and 1116 show that the shelf north of the motunau fault is underlain by complexly deformed sediments faulting and folding continue in this area today as evidenced by the presence of deformed late pleistocene strata and by the distribution of earthquake epicentres within the marlborough plate boundary zone the five major strike slip faults delimit four substantial blocks or microplates 20 60 km wide and up to 220 km long from north to south these are the spenser inland kaikoura seaward kaikoura and conway blocks respectively kaikoura sequence sediments are most strongly deformed near the margins of the blocks and their subsidiary fault systems within each microplate deformation is restricted to moderate folding and faulting the overall structural pattern being consistent with dextral movement on the boundary faults the available marine geologic and geophysical data suggest that subduction of the pacific plate may have propagated southwards during the late neogene causing successive activation of the marlborough faults today subduction is occurring right to the southern head of the hikurangi trough where the motion is transferred to the motunau fault system since earthquake epicentres only reach to intermediate depths beneath the southern part of the conway microplate and since the motunau fault system is not such a continuous physiographic features as faults further north it is likely that this southern margin to the plate boundary zone is still actively developing

physical stratigraphy and sedimentology of the late pleistocene holocene tiber delta depositional sequence the tiber delta lies on the passive continental margin of central western italy the tiber delta is a late pleistocene holocene sedimentary succession and constitutes an incomplete high frequency depositional sequence 4th or 5th order which developed from the last post glacial rise in sea level to the present stillstand it is bound by a type 1 basal unconformity which cuts pleistocene deposits five depositional systems have been identified 1 coastal barrier lagoon 2 shelf transition 3 fluvial braided 4 tiber lagoonal deltas t1 t2 t3 and 5 tiber wave dominated delta the first four systems constitute the transgressive system tract tst which is characterized by a retrogradational parasequences set while the fifth system represents the highstand system tract hst characterized by only one parasequence progradational the evolution of these depositional systems has been mostly controlled by sea level rise which was not continuous but punctuated by eight minor stillstands and rapid rises this mechanism of sea level change led to the formation of parasequences that developed within the depositional systems from a palaeogeographical point of view the present tiber delta area was mainly characterized by a coastal barrier lagoon and tiber lagoonal deltas t1 t2 t3 which migrated landwards during the sea level rise throughout the time of the present stillstand the t3 lagoonal delta prograded rapidly into the lagoon reaching the coastal barrier and the lagoon was replaced first by marshes and then by the alluvial plain finally the tiber river overcame the littoral barrier supplying the coast giving rise to the present wave dominated delta

local disequilibrium of plagioclase in high temperature shear zones of the ivrea zone italy microstructural and chemical analysis of plagioclase in 20 superficially similar amphibolite facies ductile shear zones in metagabbors and amphibolites of the ivrea zone in italy reveals significant differences in an and ba contents plagioclase which was deformed at p t conditions lower than those of the wall rocks occurs in the following four different microstructural situations with different chemical compositions i relatively undeformed porphyroclasts ii dynamically recrystallized grains and subgrains rimming the porphyroclasts iii infill of microcracks cross cutting the porphyroclasts and iv fine grained recrystallized grains in the matrix of the shear zones the differences in the an and ba contents are caused by partial chemical equilibration of plagioclase in the shear zones during and partly after deformation changes in an and ba contents were caused by fluid assisted grain boundary migration recrystallization as well as by solid state diffusion while fluid activity was high the relation between the composition and microstructures of the plagioclase in the shear zones indicates that in the different shear zones fluids ceased to be active during different stages in the late shear zone deformation history the interpretation of the variations in composition and microstructures reveals that only grains that developed by grain boundary migration recrystallization and that are not adjacent to porphyroclasts reflect p t conditions during the dominant shear zone deformation

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

marine ice sheet decoupling as a mechanism for rapid episodic sea level change the record of such events and their influence on sedimentation abstract unlike terrestrial ice sheets marine ice sheets display more sensitivity to sea level than to climate and they are capable of rapid mass wasting this mass wasting involves ice shelf decoupling from the sea floor and rapid collapse followed by drawdown of the ice sheet glaciologists argue that the marine ice sheet decoupling mechanism could cause sea level rises of a few meters within several hundred years information regarding late wisconsinan holocene glacial history suggests that ice sheet deterioration did not occur at a steady rate studies of the antarctic continental shelf indicate ice sheets grounded over large portions of the shelf during the late wisconsinan glacial maximum and that their retreat from the continental shelf was rapid a study of the trinity sabine incised valley of the texas continental shelf yields a continuous record of holocene sedimentation and sea level change paired upper bay and tidal inlet estuarine systems reflect periods when relative sea level was either at a still stand or slowly rising the flooding surfaces of back stepping parasequences reflect periods of rapid sea level rise large sand bodies on the adjacent shelf used to derive previous sea level curves for the region may represent former shoreline deposits but they also show extensive reworking therefore the curves generated from studies of these sand bodies are inaccurate marine ice sheets have existed in antarctica since at least the late eocene so this mechanism for rapid sea level rise has been active throughout much of cenozoic time as well as during older glacial episodes

dynamic recrystallization of feldspar a mechanism for ductile shear zone formation feldspar aggregates experimentally deformed in the dislocation creep regime undergo dynamic recrystallization because recovery is difficult due to the limited climb of dislocations recrystallizing aggregates have a lower strength because of the cyclic production of small strain free grains and they develop a strong preferred orientation consistent with that observed in mylonites thus recrystallization accommodated dislocation creep may be responsible for the grain size reduction and strain softening that lead to the formation of many mylonites and ductile shear zones

late quaternary depositional architecture of po and tevere river deltas italy and worldwide comparison with coeval deltaic successions abstract po and tevere rivers form two of the most important deltas of the whole mediterranean area detailed investigations have been carried out in the last decade beneath the present delta plains of these two river systems using borehole data correlation with the aid of radiocarbon dates and other dating methods pollens archaeology a detailed sequence stratigraphic framework has been constructed in both areas especially for the last glacial interglacial cycle regional subsidence combined with short term sea level fluctuations of relatively high amplitude played a fundamental role in creating subtracting accommodation during the long phase of falling sea level which followed the tyrrhenian substage 5e transgressive event a discontinuous record of this phase is present in the subsurface of the po plain whereas poor or no preservation has been detected in the tevere area progradational lowstand wedges accumulated during the last glacial maximum mostly in the central part of the basins far from the present deltas and are lacking in the study areas where a hiatal surface is invariably recorded below the transgressive deposits glacioeustasy exerted a major control on sedimentation in both areas during the latest pleistocene holocene sea level rise infilling of fluvial valleys and rapid landward migration of barrier lagoon systems in the context of wave dominated estuaries characterized the transgressive phase in both po and tevere systems in place drowning and transgressive submergence mechanisms of barrier migration were effective predominantly between 13 5 and 9 ka bp in contrast shoreface retreat was dominant in the late transgressive phase the maximum flooding surface mfs can be traced physically from continental to marine deposits and has similar characteristics in the po and tevere river systems being marked by peat layers or lagoonal deposits at landward locations and by distinctive lithological characteristics and micro and macrofossils assemblages basinwards above the mfs the early highstand systems tract records initially the filling of the lagoons followed by the rapid progradation of wave dominate delta systems and flanking strandplains autocyclic processes such as distributary channel avulsion delta lobe abandonment and local subsidence due to sediment compaction were the fundamental controlling factors on sedimentation during deposition of the hst the stratigraphic architecture of the post glacial po and tevere delta complexes closely resembles the basic facies successions documented from coeval deposits of wave dominated and wave influenced clastic coasts both locally within the mediterranean area and in other parts of the world our study emphasizes however some additional features and major differences with previously published depositional models including i the development of backstepping wave dominated estuaries during transgression ii consistent changes through time in the mechanism of barrier migration iii a later construction of the delta systems with respect to what traditionally considered

post glacial sea level control and sequence stratigraphy of carbonate terrigenous sediments wanganui shelf new zealand abstract shallow marine mixed carbonate terrigenous sediments have been accumulating in water depths of 20 110 m on wanganui shelf central western new zealand during the latest quaternary post glacial sea level rise since about 18 000 years bp cores show an upward change from coarse mostly terrigenous dominated sands and gravels to shell rich sediments and then to terrigenous dominated muddy very fine sands and sandy muds these post glacial carbonate terrigenous sediments are a modern analogue for similar episodes of cyclothemic shelf deposition that characterise onland plio pleistocene sections in central western new zealand like their ancient counterparts the latest quaternary sediments can be interpreted in a sequence stratigraphic context a transgressive systems tract 4 15 m thick overlies a transgressive erosion surface evident on seismic reflection records and is represented by slightly shelly coarse sands and gravels at the base of several cores and as palimpsest surficial deposits on the modern shallow shelf out to a depth of about 50 m the overlying shelly deposits both shell rich and matrix rich are equivalent to mid cycle or backlap shellbeds described elsewhere they comprise a diverse in situ or locally transported bivalve molluscan and bryozoan biota typical of temperate latitude cool water carbonate shelf facies these condensed section shellbeds are up to at least 1 5 m thick gradationally overlie the transgressive sediments in cores and occur as modern surficial shelf facies between about 25 and 100 m water depth cores are locally capped by up to a few metres of terrigenous sands or muds that represent highstand systems tract deposits fed onto the shelf from opposing onshore and offshore directions in the nearshore region north island derived felsic fine sands are beginning to prograde seawards westwards across the shellbeds while in the offshore zone south island derived micaceous very fine sands and muds are encroaching upon and covering the shellbeds from the west and south

compositional changes of minerals associated with dynamic recrystallizatin the rate of compositional and isotopic exchange between minerals may be enhanced significantly if the rock is deformed simultaneously the enhanced exchange rate may result from a reduction in grain size shorter distance for volume diffusion dissolution and growth of grains by diffusion creep pressure solution or the movement of high angle grain boundaries through strained grains during recrystallization in the dislocation creep regime the migration of high angle grain boundaries provides high diffusivity paths for the rapid exchange of components during recrystallization the operation of the latter process has been demonstrated by deforming aggregates consisting of two plagioclases an1 and an79 at 900 c 1 gpa confining pressure and a strain rate of 2x10 6s 1 the polygonal recrystallized grains were analyzed using an analytical transmission electron microscope and have a variable but often intermediate composition at the conditions of these experiments the volume interdiffusion rate of nasi caal is too slow to produce any observable chemical change and microstructural chemical relations indicate that the contribution from diffusion creep was insignificant except for initially fine grained 2 10 m aggregates these results indicate that strain induced recrystallization can be an effective mechanism for enhancing the kinetics of metamorphic reactions and for resetting the isotope systematics of minerals such as feldspars pyroxenes and amphiboles

episodic rapid sea level rises on the central mediterranean shelves after the last glacial maximum a review abstract submerged palaeo shorelines on the central mediterranean shelves identified from high resolution seismic profiles and bathymetric data mark distinct water depths at which sea level stationed for a period of time during the relative sea level rise that followed the last glacial maximum lgm the shorelines are commonly represented by palaeo coastal cliffs and barrier beaches that lie today at water depths between 100 m and 70 m and between 65 m and 40 m in most places irrespective of the different tectonic contexts even in the presence of significant vertical rates these morphological features are thought to have been drowned during melt water pulses 1a and 1b which occurred between 15 and 10 ka the evidence presented here confirms drowned shorelines documented elsewhere at similar water depths and shows that melt water pulses have punctuated the post glacial relative sea level rise with rates up to 60 mm yr for a few centuries the identification of morphological features related to melt water pulses in the central mediterranean sea has important implications to improve our knowledge on episodes of rapid glacio eustatic sea level rise this issue is critical to be able to forecast future sea level rises in the mediterranean which is characterized by densely populated coasts and important coastal infrastructures

sea level controls on the post glacial development of the great barrier reef queensland abstract the central great barrier reef is situated on a 125 km wide continental shelf with a shallow shelf break at ca 70 m in consequence the earlier post glacial reef tract was confined to a narrow fringing belt along the present upper slope and outer shelf the reef province only started to assume its modern dimensions after ca 10 ky b p when sea level stabilised at depths around 28 m reef growth since 18 ky b p has been controlled by the episodic nature of the post glacial transgression being related to shorelines s8 to s1 developed at estimated eustatic depths and ages of 114 m 18 ky b p 88 m 17 ky b p 75 m 15 ky b p 56 m 12 ky b p 45 m 11 ky b p 39 m 10 ky b p 28 m 9 5 ky b p 23 m 9 ky b p 9 m 7 5 ky b p and 0 m 6 5 ky b p rates of sea level rise as high as 12 m ky 1 occurred between stillstands outpacing coral growth response and resulting in many mid outer shelf reefs being drowned in situ

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

the nature of the pre holocene surface john brewer reef with implications for the interpretation of holocene reef development abstract seismic reflection profiles trace out a steep sided antecedent platform assumed to be the holocene pleistocene interface beneath the post glacial holocene coralline and sediment veneer of john brewer reef a small mid shelf reef within the central great barrier reef province this platform defined by a semi continuous seismic reflector is characterised by three essentially planar surfaces at 20m 32 m and 40 m depth with respect to present low water datum the 20 m surface which exhibits a maximum relief of 2 m is extensive and is postulated to represent either a senile reef which grew to maturity most probably during the 50 kyr interstadial or the erosion and concurrent infilling during this phase of a near flat reefal structure which dates from an earlier 20 m interstadial the deeper surfaces are less extensive that at 32 m is considered to represent a fringing reef which became established on the flanks of the antecedent platform during a brief late pleistocene sea level stillstand the 40 m surface appears to be predominantly erosional in origin and also of late pleistocene age whilst these surfaces are sites of major coral growth holocene reef development has occurred largely independent of antecedent platform morphology present reef morphology reflects the interaction between the rate of post glacial sea level rise prevailing hydrodynamic conditions and biological activity and bears no resemblance to that of the underlying antecedent surface the present morphology of john brewer reef is consistent with a continuous post glacial sea level rise

syndeformational recrystallization dynamic or compositionally induced dynamic recrystallization in the strict sense of the term is the reconstitution of crystalline material without a change in chemical composition driven by strain energy in the form of dislocations driving potentials additional to internal strain energy may contribute to the recrystallization of naturally deformed minerals which form solid solutions such as feldspar amphiboles and pyroxenes if they change their composition during recrystallization to estimate the relative importance of these driving potentials the chemical composition of porphyroclasts and recrystallized grains of plagioclase clinopyroxene and hornblende have been investigated in samples from a high grade shear zone of the ivrea zone italy the plagioclases show two different recrystallization microstructures bulging recrystallization at grain boundaries and discrete zones of recrystallized grains across porphyroclasts probably involving fracturing deformation took place under amphibolite facies conditions on a retrograde p t path porphyroclast and recrystallized compositions from bulging recrystallization microstructures differ only in their or content and yield a g between mean host grain and mean recrystallized grain composition at fixed p t conditions of approximately 5 joules 10 4 m3 extreme compositional variations yield approximately 60 j 10 4 m3 the increase of free energy due to dislocations calculated for common glide systems in plagioclase are on the order of 100 joules 10 4 m3 for high values of dislocation densities of 1014 m 2 thus the effect of chemically induced driving energies on grain boundary velocity appears small for mean compositions but may be as great as that of deformational energies for larger chemical differences in the other type of microstructure porphyroclasts and recrystallized grains in discrete zones differ in their anorthite content the maximum g induced by the compositional disequilibrium is on the order of 100 j 10 4 m3 this maximum value is of the same magnitude as the g derived from high dislocation densities of 1014 m 2 the resulting combined g is approximately twice as high as for deformational g alone and heterogeneous nucleation may become a feasible recrystallization mechanism which is evident from the microstructures the recrystallization mechanism depends on the nature of the driving potential grain boundary migration gbm and heterogeneous nucleation can release gibbs free energy induced by compositional disequilibrium whereas this is not likely for subgrain rotation therefore only gbm and heterogeneous nucleation may link metamorphism and deformation so that syndeformational recrystallization may represent a transitional process ranging from dynamic recrystallization to metamorphic reaction

underwater mapping of late quaternary submerged shorelines in the western mediterranean sea and the caribbean sea abstract underwater mapping of sea floor profiles using the self contained underwater breathing apparatus was carried out along the rocky coasts of provence in southern france west corsica and the isle of elba in italy an analysis of 150 underwater profiles in these regions has provided a sequence of sub aerial erosion notches at common depths of 11 17 25 35 45 55 and 100 m because notches at similar depths have also been found in the french west indies these notches are suggested to have been formed by the same lower eustatic sea levels during the late quaternary the occurrence of submerged sub aerial erosion notches may indicate uplift and or subsidence in tectonically active coasts

the sedimentary record of the post glacial transgression on the gulf of cadiz continental shelf southwest spain abstract four seismic units ta to td have been identified from the analysis and interpretation of high resolution seismic profiles in a sector of the gulf of cadiz shelf they constitute a composite seismic unit attributed to the transgressive systems tract tst of the last depositional sequence the earliest transgressive unit was deposited on the outer shelf and represents the distal facies of a coastal deposit a process of shelf partitioning seems to have occurred during the formation of the three later transgressive parasequences the shelf sector offshore from the guadiana river mouth was a high energy environment dominated by storm events by contrast the shelf sector offshore from the donana national park was a low gradient shelf where large barrier island and lagoon systems were formed the sparse occurrence of marine deposits within the tst is a consequence of the episodic nature of the sea level rise the generation and preservation of these transgressive deposits results from the interaction of the following controlling processes 1 relative sea level rise the formation of coastal transgressive deposits is related to intervals of reduced sea level rise or stillstands within a period of continuous sea level rise those sea level changes were probably driven by short term periods of colder climate during the late pleistocene holocene deglaciation the younger dryas interval is the most widely recognised climatic event of this type but probably other events of similar characteristics had the same effect on the glacio eustatic sea level rise 2 sediment supply changes short lived climatic events probably also involved changes in the sediment supply to the continental shelf due to changes in erosion rates and river regimes of the river basin hinterlands 3 effect of the paleophysiography paleogeography the sedimentary environments differentiation processes are associated to the formation of an exposed coastal promontory offshore from the guadiana river mouth and a semi protected embayment offshore from donana national park this coastal configuration was controlled by previous tectonic evolution and influenced the non uniform landward migration of the coastline

continuous estimation of 3 d reflector orientations along 2 d deep seismic reflection profiles abstract interpretation of 2 d deep seismic reflection data can be limited by the recording of out of plane reflections that cannot be readily distinguished from those originating beneath a seismic line here i present a method analogous to semblance velocity analysis that utilizes varying source receiver azimuths to derive continuous estimates of 3 d reflector orientations along onshore 2 d reflection profiles for each zero offset time within a common depth point supergather the semblance is calculated along 3 d travel time curves and the dip and strike of the most coherent reflection is determined relative errors in these angles are derived from the range of travel time curves that have semblance values greater than a specified fraction for example 90 of the maximum the method is illustrated using a section from line 10ga yu1 from the youanmi terrane of the yilgarn craton in australia in which the original field data have been replaced with synthetic in line and cross line reflections reflector orientations are generally well recovered where the range of available source receiver azimuths is greater than 20o but the method fails at lower ranges where the seismic line is almost linear and this behavior is also observed in analysis of the field data nevertheless when using a realistic 1 d velocity function the orientation of upper crustal shear zones can be readily determined and on unmigrated sections subhorizontal sills can be distinguished on the basis of their geometry from the mid crustal reflectivity in future surveys reflector orientations can be determined along the near linear sections of a seismic profile by deploying additional receivers perhaps as cross line recording spreads to supplement the limited range of azimuths available from the in line acquisition the method can in principle be extended to marine reflection surveys and more complex sub surface velocity models