palaeomagnetism of red beds from the kimberley group western australia implications for the palaeogeography of the 1 8 ga king leopold glaciation abstract the 1 8 ga king leopold glaciation in northwestern australia is recorded in the kimberley basin by subglacial erosional forms cut in an unconformity surface at the top of the speewah group and buried by glaciofluvial deposits at the base of the king leopold sandstone the lowest formation of the kimberley group the glaciofluvial deposits are conformably overlain by texturally mature locally glauconitic quartzarenite of shallow marine origin implying that glaciation occurred near sea level palaeomagnetic data for five sites 29 specimens in the hematite bearing elgee siltstone of the upper kimberley group in the northeastern kimberley basin gave a dip corrected mean direction of declination d 95 4 inclination i 13 8 95 9 7 indicating a palaeolatitude 7 0 5 3 5 0 results for red beds from five sites 28 specimens in the conformably overlying pentecost sandstone gave a dip corrected mean direction of d 94 1 i 13 0 95 11 7 6 6 6 4 5 9 combining our data for the elgee siltstone and pentecost sandstone with results for the elgee siltstone in the southeastern kimberley basin li z x 2000 palaeomagnetic evidence for unification of the north and west australian cratons by ca 1 7 ga new results from the kimberley basin of northwestern australia geophysical journal international 142 173 180 yielded a dip corrected mean direction for 17 sites of d 93 5 i 15 1 95 4 4 palaeolatitude 7 7 2 3 and an overall pole position at latitude p 5 4 s longitude p 211 8 e with confidence semi axes dp 2 3 and dm 4 5 a positive fold test at 99 confidence was obtained for the combined data for the 17 sites the basinwide concordance of results for the elgee siltstone and the positive fold test argue for an early magnetisation acquired prior to late palaeoproterozoic initial folding of the kimberley group and close to the time of deposition our results imply a low palaeolatitude for the kimberley group and the king leopold glaciation palaeomagnetic data for the 1 822 ga plum tree creek volcanics in the pine creek orogen to the east of the kimberley basin are consistent with northwestern australia being in low palaeolatitudes during the late palaeoproterozoic hence the enigma of glaciation near sea level in low palaeolatitudes which marks the neoproterozoic and early palaeoproterozoic applies also to the late palaeoproterozoic red beds from the lansdowne arkose of the speewah group also were studied but only directions ascribable to tertiary regolith weathering processes were found similar findings for the late palaeoproterozoic mcarthur basin in northern australia suggest some units in that basin also record tertiary regolith processes

some isotopic constraints on the evolution of the granulite and upper amphibolite facies terranes in the eastern musgrave block central australia abstract the central to eastern musgrave block central australia consists of the meso to neoproterozoic fregon and mulga park subdomains that are separated by a zone of mylonites and pseudotachylytes known as the woodroffe thrust the subdomains were previously considered to have undergone different geological histories but the differences relate mainly to metamorphic grade the fregon subdomain attained at least transitional granulite facies metamorphic conditions and the mulga park subdomain reached upper amphibolite facies felsic gneisses from both the fregon and mulga park subdomains contain zircons that are structured with euhedral centres overgrown by round elongate rims ion microprobe u pb analyses of the cores yield ages of 1557 24 and 1554 28 ma respectively and are interpreted to represent the time of igneous crystallization these ages place a maximum age constraint on the deposition or emplacement of the gneiss precursor high grade metamorphism grading from upper amphibolite to granulite facies took place between 1200 and 1150 ma and prior to the intrusion of several granitoid suites at around 1150 ma the kulgera adamellite and ayers ranges adamellite granitoid suites of the fregon subdomain yield ion microprobe u pb crystallization ages of 1150 12 and 1152 11 ma respectively a concordant u pb isotope dilution analysis on the ayers ranges adamellite yields a more precise age of 1152 3 ma the porphyritic suite intruding the mulga park subdomain yield an ion microprobe u pb magmatic age of 1159 20 ma these emplacement ages indicate extensive grenvillian felsic magmatism not previously recognized in australia the woodroffe thrust formed during a period of substantial crustal shortening the petermann orogeny 550 ma when the fregon subdomain was thrust onto the mulga park subdomain synkinematic muscovite and biotite record k ar and rb sr ages between 560 and 520 ma this petermann event is not recorded in the fregon subdomain due to confinement of the strain and associated mineral recrystallization to the underlying mulga park subdomain we suggest that the granulites were not exposed prior to the petermann orogeny as the basal quartzites of the amadeus basin occur only on the amphibolite facies mulga park subdomain

quartz grains reveal sedimentary palaeoenvironment and past storm events a case study from eastern baltic abstract sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess in this study we use several proxies from sediment of the holocene thermal maximum at coastal lake lilaste latvia we focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments we then use this as a proxy for potential storm transport and combine with information on granulometry diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone grains representing very energetic subaqueous environment similar to storm events are also present terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains during drier and colder conditions an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr bp marine and terrestrial conditions alternated between 7800 and 6000 cal yr bp storm induced grains were likely deposited three times at 7300 cal yr bp 6600 6400 cal yr bp and 6200 6000 cal yr bp overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr bp except of the last portion of terrestrial induced sediment at 4100 cal yr bp

ostracods from a marmara sea lagoon turkey as tsunami indicators abstract a 352 cm long sediment core from hersek lagoon gulf of izmit was investigated for its ostracod species composition in order to evaluate the potential of ostracods to detect tsunami deposits in coastal environments the gulf of izmit is the eastern bay of the marmara sea which is tectonically controlled by the north anatolian fault ostracod shells are rare in the lower third of the core which probably represents a coastal wetland environment according to radiocarbon dating of terrestrial plant remains this unit was deposited between ad 500 and ad 800 above ostracod shells are abundant and dominantly monospecific composed almost exclusively of the widespread brackish water ostracod cyprideis torosa this almost monospecific occurrence indicates the establishment and maintenance of the hersek lagoon after ad 800 three distinct layers of mollusc shells and fragments contain ostracod shells of marine and to a lesser extent non marine origin in addition to those of c torosa the shell layers are further characterized by significant maxima in total ostracod shell numbers the high concentration of ostracod shells the higher species numbers and the mixture of marine lagoonal and non marine ostracod shells shows that shell layers were formed as high energy deposits resulting from tsunamis or large storms in the marmara sea the partial occurrence of non marine ostracod shells in the shell layers possibly indicates that tsunamis with extensive run ups and significant backwash flows caused the high energy deposits rather than large storms the investigated sediments show that lagoonal ostracods can serve as good proxies for tsunamis or large storms through significant variations in total shell numbers species numbers and the mixing of shells of different origin

microtextural characteristics of quartz grains transported and deposited by tsunamis and storms article i nfo the complex transport and depositional processes associated with tsunamis and storms and the peculiarities of local inundation present questions associated with the recognition and differentiation of the sedimentary signature of these events this work presents a study of quartz grains transported and deposited by tsunami and storm waves with the objective of identifying specific microtextural signatures caused by high energy marine inundations and to correlate them with their principal sedimentary sources in this empirical study 1150 quartz grains 78 samples and their microtextural signatures were observed analyzed and classified using scanning electron microscope photomicrographs the results suggest that although no specific microtextural signature is associated with high energy inundations there are strong increases in the percent age of fresh surfaces and percussion marks when compared with the potential source material moreover tsunami and storm grains present the greatest microtextural variance among all the grains analyzed never theless specific local conditions and sediment concentrations constrain the microtextural implications on tsunami or storm grains one laboratory experiment was designed to test microtextural implications in grains subjected to variable velocities sediment concentration and time the surface microscopic signature in quartz grains of high energy events further contributes to the development of more efficient sedimentological criteria to identify deposits associated with tsunami and storm events

did late palaeoproterozoic assembly of proto australia involve collision between the pilbara yilgarn and gawler cratons geochronological evidence from the mount barren group in the albany fraser orogen of western australia abstract the mount barren group which crops out on the southern margin of the yilgarn craton has been considered an allochthonous synorogenic sequence to a mesoproterozoic 1300 ma collision between southwestern australia southeastern australia and eastern antarctica during assembly of east gondwana reassessment of its stratigraphic geometry confirms the historical perspective that nonconformable and faulted contacts are preserved on autochthonous archaean orthogneiss of the yilgarn craton emphasising that it is not an allochthonous sequence shrimp u pb dating of early diagenetic xenotime establishes a late palaeoproterozoic 1696 7 ma depositional age for the mount barren group thereby negating a mesoproterozoic synorogenic origin the mount barren group now correlates in time with strike slip sequences in the capricorn orogen approximately 1000 km to the north and which were a post collisional response to 1750 ma sinistral transform collision between the pilbara and yilgarn cratons shrimp u pb detrital zircon geochronology of the mount barren group therefore has an important role in establishing if pilbara yilgarn transform collision were either independent of or a component in the late palaeoproterozoic assembly of a proto australian continent detrital zircon age data from four samples of different sandstone beds in the mount barren group define complex age spectra composed of seven significant provenance age subpopulations comparison to age spectra from provinces with a possible geotectonic link to the yilgarn craton indicates that either the pilbara craton or the gawler craton was the source terrain a barrier to a dispersal system link to the pilbara craton points to the gawler craton as the source a provenance link that was also made for the now redundant 1300 ma scenario the 1696 7 ma depositional age and zircon provenance analysis support a contentious hypothesis involving coeval collisions between the pilbara yilgarn and yilgarn gawler cratons during assembly of a proto australian continent some 500 400 million years earlier than envisaged by other reconstructions

remanent magnetization mapping a tool for greenfields magmatic ni cu pge exploration undercover part 1 abstract there are many challenges for greenfields exploration particularly in vast sparsely populated partially covered terrains e g a paucity of prior exploration data and difficulties in gaining access to land however in many cases good aeromagnetic coverage is freely available and for some styles of mineralization e g magmatic ni cu pge aeromagnetic data alone can provide critical insights into the age size and depth of multiple targets across large regions early in the exploration life cycle this study investigates whether an understanding of remanent magnetization from three suites of mafic intrusions exposed in the huckitta area nt australia can be utilized to provide a first pass exploration tool for exploration under shallow cover to the east the study demonstrates that although the measured remanent magnetization vectors present were complex in some cases the majority are sub parallel oriented steep down to the south which implies a common mode of acquisition it was found that the magnetizations were acquired during the alice springs orogeny ca 450 300 ma with the dominant magnetization occurring at ca 330 ma therefore the magnetizations present do not relate to cooling of the parent magmas but rather to cooling of lower crustal rocks from temperatures above the curie point 580 c during exhumation of the host terrain whilst this knowledge does not allow discrimination of the three suites remotely based purely on their remanent magnetization vectors the recognition of a common magnetization vector present in all mafic rocks does allow us to better map mafic rocks under cover and better constrain magnetic modelling and exploration targeting as discussed in the second paper

warakurna large igneous province a new mesoproterozoic large igneous province in west central australia coeval mafic igneous rocks emplaced rapidly over 1 5 3 10 6 km 2 in western and central australia represent the erosional rem nants of a late mesoproterozoic large igneous province named here the warakurna large igneous province shrimp u pb dating of rocks separated by as much as 1500 km indicates that the main episode of magmatism occurred between 1078 and ca 1070 ma the warakurna large igneous province includes layered mafic ultramafic intrusions and mafic to felsic volcanic rocks and dikes in central australia a 1000 km long mafic sill province in western australia and several swarms of mafic dikes the large areal ex tent and short duration imply emplacement above a mantle plume head despite their wide separation the mafic rocks have similar mid oceanic ridge basalt normalized trace element patterns and rare earth element characteristics west directed paleocurrents westward radiating dike swarms and the occurrence of high mg rocks indicate that the center of the plume head was located be neath central australia other late mesoproterozoic large igneous provinces in the laurentia and kalahari cratons appear to be significantly older than the warakurna large igneous province in australia and thus are unlikely to be related to the same mantle plume head

sedimentology and paleontology of a tsunami deposit accompanying the great chilean earthquake of february 2010 abstract at pichilemu in the northern third of the rupture area of the moment magnitude scale mw 8 8 2010 chile earthquake deposits of the tsunami accompanying the earthquake consist of a lower layer of medium to fine sand mean grain size of 200 m containing rock clasts overlain by a thin silty very fine sand mean grain size of 125 m layer based on a sedimentological model most 90 of the deposit is finer than 401 408 m suggesting tsunami flow velocities were between 7 m s and 13 5 m s ostracods were common in the upper layer along with a small number of broken benthic foraminifera and a single planktonic foraminifera diatoms were abundant throughout species assemblages represent a mixture of diatoms from differing environments life forms and substrate preferences we attribute the mixed assemblages to turbulence within the water column during tsunami inundation with erosion of beaches and salt marshes followed by redeposition of sand and mud inland breakage of fragile diatom valves in the lower layer may also support transport by turbulent flow a higher abundance of diatom species with mud substrate preferences in the upper layer implies a decrease in flow velocity from lower to upper layers

palaeomagnetic evidence for unification of the north and west australian cratons by ca 1 7 ga new results from the kimberley basin of northwestern australia summary a palaeomagnetic study of the elgee formation red siltstones and shales in the palaeoproterozoic kimberley basin of northwestern australia has been carried out all seven sampling sites revealed an extremely stable magnetic remanence carried by haematite the age of the formation is confined by precise shrimp u pb ages of early diagenetic xenotime from rocks both above and below it to be 1704 7 14 ma but this may represent a minimum age the youngest detrital zircon grains in the underlying formation provide a maximum age of 1786 14 ma for the formation the extreme stability of the remanence the dissimilarity of the remanent direction from expected younger palaeomagnetic directions and the lack of regional overprint in the 1790 4 ma hart dolerite just north of the study region support a primary origin for the remanence a marginally positive fold test also supports a primary origin the mean direction of d 92 2 i 14 9 a 95 6 4 gives a palaeopole at 4 4 s 210 0 e with dp 3 3 dm 6 5 this pole a previously reported palaeopole from the hart dolerite and ca 1700 ma overprint poles from the pilbara craton all agree with palaeopoles of similar ages from the mcarthur basin of northern australia palaeomagnetic results thus suggest that the north and west australian cratons were possibly joined together by approximately 1 7 ga

coastal stratigraphies of eastern bonaire netherlands antilles new insights into the palaeo tsunami history of the southern caribbean abstract a sediment record of three alluvial sites along the east and northeast oriented shore of bonaire netherlands antilles provides evidence for the recurrence of several extraordinary wave impacts during the holocene the interpretation of onshore high energy wave deposits is controversially discussed in recent sedimentary research however it represents a powerful tool to evaluate the hazard of tsunami and severe storms where historical documentation is short and or fragmentary a facies model was established based on sedimentary and geochemical characteristics as well as the assemblage and state of preservation of shells and shell fragments radiocarbon data and the comparison of the facies model with both recent local hurricane deposits and global tsunami signature types point to the occurrence of three major wave events around 3300 2000 1700 and shortly before 500 bp since i the stratigraphically correlated sand layers fulfill several sedimentary characteristics commonly associated with tsunamis and ii modern strong hurricanes left only little or even no sediment in the study areas they were interpreted as tsunamigenic however surges largely exceeding the energy of those accompanying modern hurricanes in the southern caribbean cannot entirely be ruled out the results are partially consistent with existing chronologies for holocene extreme wave events deduced from supralittoral coarse clast deposits on aruba bonaire and curacao as well as overwash sediments from cayo sal venezuela

sediments deposited by the 2004 indian ocean tsunami along the malaysia thailand peninsula stratigraphy grain size distribution and foraminiferal assemblages of pre tsunami and tsunami sediment from the indian ocean tsunami at five sites along the malaysia thailand peninsula were analyzed to gain information on tsunami sediment source and deposition style between three and five stratigraphic units were identified at each site and contained between one and three fining upward sequences reflecting waning flow or pre backwash deposition coarser sand layers reflecting uprush high energy flow separated the fining upward sequences with the exception of one site sungai burong which contained a coarsening upward sequence all contacts between the pre tsunami and tsunami sediment were sharp or erosional medium and coarse sand dominated all of the tsunami sediment deposits and often contained shell fragments foraminiferal assemblages were able to differentiate pre tsunami sediment from tsunami sediment where no lithological or grain size distribution change was evident between two and four foraminiferal zones were identified at each of the five sites and provided estimates of sediment source and wave characteristics

recognition of diagnostic criteria for recent and paleo tsunami sediments from sri lanka uncontaminated sediment from the december 26 2004 tsunami in southern sri lanka was collected from a previously empty arrack bottle stacked in a plastic case at an elevation of about 5 m above mean sea level and from several other localities the sediments were analysed for grain size distribution sediment petrography and microfossil assemblages and were compared with storm surge sediment and nearshore sediment the undiluted tsunami sediment is a brownish silty fine sand it is characterized by a particular grain size distribution and an assemblage of planktonic benthic microfossils consisting of foraminifera radiolarians and spicules storm surge and nearshore sediments are better sorted have fewer microfossils more rounded quartz grains and a higher proportion of heavy minerals influenced by references in sri lankan ancient texts to past tsunamis we searched for paleo tsunami sediments in potential locations such as the coastal depressions in borehole samples and well cuttings from soil profiles in the coastal village of peraliya we were able to recognize two paleo tsunami horizons at 30 and 75 cm below the present ground surface each consisting of brownish silty fine sand that remarkably resembled the recently deposited undiluted tsunami sediment

intra ordovician deformation in southeast ireland evidence from the geological setting geochemical affinities and u pb zircon age of the croghan kinshelagh granite the croghan kinshelagh alkali granite intrudes a cleaved volcano sedimentary sequenceon the border of counties wicklow and wexford in southeast ireland u pb dating of zircons fromthe granite indicate a mid caradoc emplacement age of 454 1 ma the duncannon group hostrocks form the southwestern end of the avoca volcanic belt a mid ordovician caradoc sequenceof acid and intermediate lavas and volcaniclastics dolerite dykes intrude the granite elsewhere in theregion dolerites are generally associated with volcanic rocks the main dl deformation within theduncannon group rocks is manifest as a steep dl cleavage generally regarded as a product of latecaledonian regional deformation in southeast ireland the croghan kinshelagh granite showsstrong geochemical coherence with subalkaline varieties of the caradoc volcanic rocks relativelyhigh th y nb and ree contents set it apart from any other known granite type in southeastireland together with the geochemical evidence the age determination of 454 ma indicates that thecroghan kinshelagh granite was generated and emplaced during ordovician volcanism in southeastireland volcanism was closely followed by penetrative deformation and emplacement of the granite the intra ordovician deformation may have been a consequence of closure of the iapetus ocean ormore localized events such as accretion on the hanging wall of the subduction zone the age of thecroghan kinshelagh granite provides an important datum for ordovician volcanism and subductionin southeast ireland

the ad 1755 tsunami deposits onshore and offshore of algarve south portugal sediment transport interpretations based on the study of foraminifera assemblages abstract tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events the accurate establishment of return periods can also be derived using sedimentological data onshore tsunami deposits have been extensively described over recent years through the application of a wide range of sedimentological proxies including micropalaeontological analysis in this work the identification of palaeotsunami evidence in both the onshore and offshore sedimentary record of south portugal was performed relying mostly on the study of foraminifera assemblages three onshore trenches and one offshore core were analyzed and imprints of the ad 1755 tsunami were observed based in the identification of allochthonous foraminiferal species increase in the number of broken abraded tests and its correlation with coarser mean grain size this was possible after micropalaeontological environmental characterization of both low energy onshore and offshore present day sedimentation regimes in the onshore record three distinct sediment transport phases were differentiated within the tsunamigenic unit the basal phase portraying the initial inundation represented by the dominance of marine foraminifera species in a highly diverse assemblage the higher energetic character of this phase was also reflected in the identification of the highest number of broken abraded tests the intermediate phase reflects an unspecified number of inundation and backwash pulses that were recognized based in the well balanced presence of estuarine brackish and marine species the sharp decrease in the diversity index and in the number of broken abraded tests the final phase recorded in the tsunamigenic unit registers the imprint of the last relevant backwash which was identified based on the dominance of estuarine brackish fauna the overlying unit is dominated by tidal marsh species demonstrating the start of the coastal system recovery phase in the offshore record it was possible to identify 2 distinct historical tsunami events ad 1755 and ad 1969 this was achieved through the identification of significant increases in coastal foraminifera species coupled with the presence of coarser layers this interpretation was sustained by indirect age estimation methods radiocarbon and 210 pb that ascribed compatible ages to the historical tsunami events the results obtained in this study stress the relevance and innovative character of this onshore and offshore multiproxy approach in the recognition and understanding of tsunami events

micropaleontology of the 2013 typhoon haiyan overwash sediments from the leyte gulf philippines abstract coastal geologic records allow for the assessment of long term patterns of tropical cyclone variability however the accuracy of geologic reconstructions of tropical cyclones is limited by the lack of modern analogues we describe the microfossil foraminifera and testate amoebae assemblages contained within overwash sediments deposited by typhoon haiyan when it made landfall on the islands of leyte and samar in the philippines on 7 november 2013 as a category 5 super typhoon the overwash sediments were transported up to 1 7 km inland at four study sites the sediments consisted of light brown medium sand in a layer

linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence summary consider a sequence of say 10 to 20 vector observations in threedimensional space it is suspected that a few subsets of consecutive observations are made up of collinear points the purpose of this paper is to construct a statistically based algorithm to find such linear segments and to assess their accuracy a similar assessment is made for coplanar sets of points this algorithm is applied here to palaeomagnetic data and is claimed to be superior to previous methods of palaeomagnetic analysis in terms of completeness and balance of analysis treatment of measurement errors and other sources of scatter criteria for identification of linear and planar sets of points and statistical rigour stability spectra with statistically based confidence limits are obtained as a by product 1 palaeomagnetic analysis background to the geometrical problem the natural remanent magnetization nrm in rocks is known in general to have originated in one or more relatively short time intervals during their formation and subsequent history i e during rock forming or metamorphic events during which nrm is frozen in stabilized by falling temperature grain growth etc the nrm acquired during each such event is a single vector magnetization parallel to the then prevailing geomagnetic field and is called a component of nrm rocks which have suffered more than one event of this kind are therefore liable to carry multi component nrm in the laboratory these components can be identified by demagnetizing the rock step by step usually by thermal alternating field or chemical demagnetization which involves the analysis of the distribution of blocking rzmperature coercivity and chemical leaching respectively resistance to these treatments is called stability of remanence and the range of treatment over which a particular component is removed is called the stability range of the component the various discrete

expanding the proxy toolkit to help identify past events lessons from the 2004 indian ocean tsunami and the 2009 south pacific tsunami article i nfo some of the proxies used to identify palaeotsunamis are reviewed in light of new findings following the 2004 indian ocean tsunami and the 2009 south pacific tsunami and a revised toolkit provided the new application of anisotropy of magnetic susceptibility ams to the study of tsunami deposits and its usefulness to determine the hydrodynamic conditions during the emplacement of tsunami sequences together with data from grain size analysis are presented the value of chemical proxies as indicators of saltwater inundation associated marine shell and or coral high energy depositional environment and possible contamination is demonstrated and issues of preservation addressed we also provide new findings from detailed studies of heavy minerals new information gathered during the unesco international oceanographic commission ioc international tsunami survey of fine onshore sediments following the 2009 south pacific tsunami is presented and includes grain size chemical diatom and foraminifera data the tsunami deposit varied ranging from fining upward sand layers to thin sand layers overlain by a thick layer of organic debris and or a mud cap grain size characteristics chemical data and microfossil assemblages provide evidence for marine inundation from near shore and changes in flow dynamics during the tsunami

tsunami deposits in holocene bay mud in southern kanto region pacific coast of central japan abstract tsunami have probably deposited sand sheets that are intercalated in holocene bay floor mud exposed on the boso and miura peninsulas facing the convergent boundary of the pacific philippine sea and eurasian plates we have identified seven sand sheets at four drowned valleys and correlated these by 137 radiocarbon dates of shells and wood the sheets consist of poorly sorted muddy sand and well sorted sand layers in fining upward sequences containing abundant transported shells rip up clasts and wood fragments the sheets erosionally overlie bioturbated bay floor mud that contains molluscan shells in life position most of the sheets are less than 20 cm thick and rarely more than 50 cm thick some molluscan shells are older in these layers than in underlying mud both landward and seaward paleocurrents are shown in a few cases by imbrication of shells and by low angle wedge shaped lamination at least five of the sand sheets contain molluscan fossils derived from rocky coasts or shore platforms although they intercalated in mud deposited within bays at depths of 10 15 m two other sand sheets are dominated by open seashore ostracode assemblages although they were deposited in the brackish inner bay and muddy central bay five of the layers may correlate with emergences recorded by nearby holocene marine terraces these correlations suggest that great earthquakes triggered the inferred tsunami the tsunami occurred at intervals of 300 2000 years beginning about 10 000 years ago

geological and palaeomagnetic significance of the kulgera dyke swarm musgrave block nt australia summary the kulgera dyke swarm consists of olivine tholeiites which have intruded late proterozoic transitional granulite gneisses and granites of the eastern musgrave block in central australia preliminary rb sr results suggest that the dolerites were emplaced at 1054 f 14ma in addition a rb sr age of 1060 f 10ma on a biotite from a pegmatite indicates thermal resetting of the country rock minerals during dyke emplacement palaeomagnetic investigations of the dykes yield a primary thermoremanent magnetization direction corresponding to a palaeomagnetic pole at 17 s 266 e ag5 12 in addition to this primary magnetization an overprint component was present in many of the samples providing a palaeomagnetic pole at 30 s 138 e ags 24 which is similar to previous results from other central australian rocks affected by the alice springs orogeny the results extend the area of influence of the carboniferous alice springs orogeny southward into the musgrave block further the results provide no evidence for an earlier late proterozoic petermann orogeny affecting the musgrave block in the kulgera region however the possibility that a petermann orogeny thermal overprint has been erased by the alice springs orogeny cannot be dismissed

potential predecessors of the 2004 indian ocean tsunami sedimentary evidence of extreme wave events at ban bang sak sw thailand abstract where historical records are short and or fragmentary geological evidence is an important tool to reconstruct the recurrence rate of extreme wave events tsunamis and or storms this is particularly true for those coastal zones around the indian ocean where predecessors of similar magnitude as the 2004 indian ocean tsunami iot have not been reported by written sources in this context the sedimentary record of the holocene coastal plain of ban bang sak phang nga province thailand provides evidence of multiple prehistoric coastal flooding events in the form of allochthonous sand beds which were radiocarbon dated to 700 500 1350 1180 and younger than 2000 cal bp the layers were assigned to high energy events of marine origin which could be either tsunamis or tropical storms by means of granulometry geochemistry vertical structure and macrofossil content although no landfall of a strong storm has occurred in the last 150 years of meteorological data recording cyclones cannot be ruled out for the last centuries and millennia however discrimination between tsunami and storm origin was mainly based on the comparison of the palaeoevent beds with the local deposit of the iot which revealed similar characteristics in regard to spatial extend and sediment properties furthermore the youngest palaeoevent correlates with contemporaneous deposits from thailand and more distant coasts hence we relate it to a basin wide tsunami which took place 700 500 years ago for the sediments of older extreme events deposited between 2000 and 1180 cal bp we found no unambiguous counterparts at other sites nevertheless at least for now they are treated as tsunami candidates

smnd mineral isochron ages of late proterozoic dyke swarms in australia evidence for two distinctive events of mafic magmatism and crustal extension two distinctive events of widespread dyke intrusion have been identified in central southern australia crystallization ages of the dykes were determined using sm nd mineral isochrons obtained by splitting clinopyroxene and plagioclase into different magnetic and density fractions respectively the stuart dyke swarm in the southern arunta inlier and the kulgera dyke swarm in the eastern musgrave inlier define essentially identical crystallization ages of 1076 33 and 1090 32 ma respectively marking the first episode of post orogenic mafic magmatism in the region two samples from the gairdner dyke swarm in the stuart shelf yield sm nd mineral isochron ages of 867 47 and 802 35 ma respectively whilst two samples from the amata suite in the central musgrave inlier 790 40 and 797 49 ma these four ages represent the second episode of mafic magmatism in central southern australia these ages allow new constraints to be placed on the timing of large scale crustal extension and formation of intracratic depositional basins in the region initial nd values of 7 8 to 6 6 for the stuart dykes and 0 7 for the kulgera dykes suggest they were derived from different mantle sources with the stuart dykes being produced from strongly enriched sources in contrast positive and relatively uniform initial nd values of 2 5 to 4 1 for the younger amata suite and gairdner dykes indicate that they were derived from relatively depleted and homogeneous mantle sources the 1076 33 ma sm nd age of the stuart dyke swarm is significantly older than its rb sr mineral isochron age of 897 9 ma previously reported suggesting mobility of rb and or sr and partial resetting of rb sr isotopic systematics this study demonstrates that reliable and relatively precise sm nd ages can be obtained for precambrian dykes despite the limited number of mineral phases available in the dykes

sedimentological and geomorphological effects of the sumatra andaman tsunami in the area of khao lak southern thailand the sumatra andaman tsunami left distinctive sedimentological and geomorphological signatures in the area of khao lak fine grained sediments predominantly layers of cohesive carbonate rich fine sandy silt with thicknesses of 1 10 cm erosionally overlying pre tsunami sandy soils and sediments represent the most common tsunami deposits in the study area petrographically they differ significantly from other coastal sediments and affiliated soils due to their grain size and corresponding clay mineral content muddy shelf sediments sub wave base are indicated as a main source the present results suggest that indications of shelf influence although varying regionally might contribute to the identification of fine grained tsunami sediments and their differentiation from storm sediments however the observed differences of tsunami sediments to soils and other coastal sediments especially with respect to carbonate mineralogy might disappear in short geological time under conditions of intensive weathering and bioturbation at cape pakarang hundreds of boulders with up to 24 tons were deposited on the foreshore and upper shoreface applying nott s earth planet sci lett 210 269 276 2003 formulas minimum flow velocities of 3 9 m s are required to transport the largest boulders the devastating tsunami effect of both onshore flow and backflow is documented by damaged human constructions geomorphological effects include intensive widening of estuary mouths and the development of erosional channels now estuary mouths are reduced and erosional channels cut off from the sea due to the formation of a post tsunami beach ridge

broad scale proterozoic deformation of the central superior province revealed by paleomagnetism of the 2 45 ga matachewan dyke swarm an extensive paleomagnetic study of the 2 45 ga matachewan dyke swarm of the north american superior province suggests that the interior of an archean shield can undergo broad scale distortion as a result of later proterozoic orogenic activity around the craton margins data collected from over 300 sites of which 137 are reported here for the first time reveal that the dykes contain a dual polarity primary remanence that varies across the swarm in both inclination and declination these regional variations are statistically significant at the 95 confidence level and cannot be attributed to remagnetization or to magnetic anisotropy inclination variation is probably due to real or apparent polar wander during the emplacement of the swarm and may in part explain the declination variation as well however for dykes within and northwest of the kapuskasing structural zone ksz a positive correlation is found between regionally averaged values of declination and dyke trend here the dykes appear to hav

palaeomagnetism of iron formation from the late palaeoproterozoic frere formation earaheedy basin western australia palaeogeographic and tectonic implications abstract oriented cores of unweathered frere formation 1 9 1 8 ga including shaly and peloidal iron formation were obtained from two holes drilled to 116 m depth on opposite limbs of an anticline in the southern earaheedy basin at the northeastern margin of the yilgarn craton anisotropy of magnetic susceptibility measurements indicated that the frere formation in this area was unaffected by regional metamorphism the predominant magnetic mineral in the iron formation is hematite but a small amount of magnetite also is present in some samples stepwise thermal demagnetisation was conducted for 263 specimens many specimens acquired spurious components of magnetisation after treatment to 300 500 c ascribable to the oxidation of siderite to magnetite on heating however other specimens displayed a stable high temperature 680 c dual polarity component a carried by hematite that gave a bedding dip corrected direction of d 314 3 i 24 8 k 38 5 95 2 6 n 78 a fold test was positive at 99 level of confidence indicating acquisition of remanence prior to stanley folding in the earaheedy basin that occurred at 1 78 ga near the end of capricorn orogenesis the presence of polarity reversals in the stratigraphic section from one drill hole and within some specimens argues for the identification of a dipole field axis and the sufficient averaging of secular variation to define a palaeopole for the frere formation located at 45 2 s 220 0 e dp 1 3 dm 2 4 component a is ascribed to a chemical remanent magnetisation crm acquired soon after deposition and indicates a palaeolatitude of 13 0 1 5 for the frere formation the frere pole plots adjacent to but is still significantly different from late to post capricorn orogeny overprint poles from the hamersley province of the southern pilbara however vertical axis relative anticlockwise rotation of 10 15 for the frere pole brings it close to these pilbara overprint poles the data imply that the earaheedy basin and possibly the yilgarn craton underwent clockwise rotation of 10 15 relative to the pilbara craton during stanley folding this finding accords with evidence for tectonic settings marked by sinistral strike slip deformation adjacent to the yilgarn pilbara cratonic boundary during deposition and subsequent folding in the earaheedy basin the data also imply that the west australian and north australian cratons were in close proximity by 1 8 ga

sedimentary record of the 1872 earthquake and tsunami at owens lake southeast california abstract in 1872 a magnitude 7 5 7 7 earthquake vertically offset the owens valley fault by more than a meter an eyewitness reported a large wave on the surface of owens lake presumably initiated by the earthquake physical evidence of this event is found in cores and trenches from owens lake including soft sediment deformation and fault offsets a graded pebbly sand truncates these features possibly over most of the lake floor reflecting the tsunami wave confirmation of the timing of the event is provided by abnormally high lead concentrations in the sediment immediately above and below these proposed earthquake deposits derived from lead smelting plants that operated near the eastern lake margin from 1869 1876 the bottom velocity in the deepest part of the lake needed to transport the coarsest grain sizes in the graded pebbly sand provides an estimate of the minimum initial tsunami wave height at 37 cm this is less than the wave height calculated from long wave numerical models about 55 cm using average fault displacement during the earthquake two other graded sand deposits associated with soft sediment deformation in the owens lake record are less than 3000 years old and are interpreted as evidence of older earthquake and tsunami events offsets of the owens valley fault elsewhere in the valley indicate that at least two additional large earthquakes occurred during the holocene which is consistent with our observations in this lacustrine record

late pleistocene raised beaches of coastal estremadura central portugal abstract we present new stratigraphic sedimentological and chronological data for a suite of tectonically raised beaches dating to marine isotope stages 5 4 and 3 along the estremadura coast of west central portugal the beach deposits are found in association with ancient tidal channels and coastal dunes pollen bearing mud and peat and middle paleolithic archaeological sites that confirm occupation of the coastal zone by neanderthal populations the significance of these deposits is discussed in terms of the archaeological record the tectonic and geomorphic evolution of the coast and correlation with reconstructions of global climate and eustatic sea level change direct correlation between the estremadura beach sections is complicated by the tectonic complexity of the area and the age of the beach deposits which are near or beyond the limit of radiocarbon dating evidence from multiple sites dated by ams radiocarbon and optical luminescence methods suggests broad synchroneity in relative sea level changes along this coast during marine isotope stage 3 two beach complexes with luminescence and radiocarbon age control date to about 35 ka and 42 ka recording a rise in relative sea level around the time of heinrich event 4 at 39 ka depending on assumptions about eustatic sea level at the time they were deposited we estimate that these beaches have been uplifted at rates of 0 4 4 3 mm yr 1 by the combined effects of tectonic halokinetic and isostatic processes uplift rates of 1 2 mm yr 1 are likely if the beaches represent sea level stands at roughly 40 m below modern as suggested by recent eustatic sea level reconstructions evidence from coastal bluffs and the interior of the study area indicates extensive colluvial fluvial and aeolian sedimentation beginning around 31 ka and continuing into the holocene these geomorphic adjustments are related to concomitant changes in climate and sea level providing context that improves our understanding of late pleistocene landscape change and human occupation on the western iberian margin

isotopic dating in metamorphic belts isotopic dating in metamorphic rocks is concerned with the timing of processes whose operation is controlled by continually changing physical conditions of these temperature has a pervasive influence and the use of physical models to elucidate the ways in which temperature is likely to vary is briefly reviewed the central concept of closure temperature is critically discussed and quantitative estimates for biotite and hornblende are evaluated in order to illustrate the factors which control closure temperatures and limit their application in practice the possibility of dating crystallization using minerals which crystallize below their respective closure temperatures is examined taking examples involving k ar rb sr sm nd and u pb analyses the indirect dating of metamorphism via structurally dated plutons is briefly considered and the problems of interpreting both discordant u pb zircon ages and rb sr whole rock isochrons in metamorphosed granites are discussed the value of near concordant zircon ages is emphasized the extent of isotopic equilibration during metamorphism specifically of sr isotopes in metasediments is shown not to be a simple function of metamorphic grade the flow of fluids produced by metamorphic reactions appears to be crucial and there is a potential for dating metamorphism using whole rock samples where such flow can he demonstrated independently the concluding discussion briefly examines existing data for the dalradian and indicates the potential for further progress using both well established and novel approaches

palaeomagnetic cleaning strategies abstract cleaning is a term used in palaeomagnetism to refer to laboratory methods designed to demagnetize preferentially the less stable components of magnetization although the diversity of methods suggests that there is a wide choice available this is illusory except in simple cases the wrong cleaning strategy may yield misleading results cleaning methods include thermal magnetic alternating field or a f low temperature chemical shock and microwave cleaning a cleaning strategy involves one or more cleaning methods applied in a specific sequence the design of a strategy is made easier with the a priori knowledge of magnetic mineralogy and granulometry or in other words rock magnetic properties although not a substitute for other rock magnetic experiments the variation of low field susceptibility with temperature k t not only provides information on magnetic mineralogy and granulometry but it also draws attention to chemical alteration that may occur during thermal cleaning apart from the rapid though reversible decrease of k associated with curie temperatures other diagnostic k t features include the low temperature about 140 c peak typical of multidomain md magnetite the high temperature hopkinson peak typical of fine grained magnetite and other magnetic minerals and the classic lepidocrocite maghemite haematite profile which is irreversible examples are given where the remanence caused by lightning can be effectively eliminated only by applying a f or low temperature lt pre treatment such remanence may be an isothermal remanent magnetization irm or a combination of irm and anhysteretic remanent magnetization arm as the unblocking temperature of relatively low coercivity md grains may extend to high temperature it is often desirable to suppress md remanence an example is given of palaeointensity determination with the without lt pre treatment the nature of the lt transition is briefly addressed in the light of a rare double low temperature peak which may reflect both the isotropic point and the verwey transition

low temperature thermal history of eastern ireland effects of fluid flow abstract a reconnaissance apatite fission track study was undertaken in eastern ireland to evaluate the low temperature thermal history of palaeozoic basement rocks outcropping adjacent to the irish sea basin on a sampling transect across the lapetus suture zone the distributions of single grain ages and track lengths indicate cooling after maximum palaeotemperatures of between 80 and 100 110 c at various times during the early tertiary about 30 45 ma although a significant component of tertiary uplift and erosion is inferred in eastern ireland from geological observations maximum palaeotemperatures are interpreted as principally due to heat advection by gravity driven groundwater flow following early tertiary uplift at about 60 ma this phase of fluid flow produced the localized remagnetization of the palaeozoic basement and overlying carboniferous limestones in north co dublin limited sampling in eastern ireland indicates extreme local heterogeneity in apatite age also characteristic of apatite fission track results from northern england thus heterogeneity requires an annealing control independent of the sample s thermal history suggested to be the individual crystal uranium content and indirectly the effects of fluid flow

argon retentivity of hornblendes a field experiment in a slowly cooled metamorphic terrane hornblende from samples of amphibolite and granitic gneiss collected within a single outcrop in the central adirondacks yield significantly different sup 40 ar sup 39 ark sub k dates of 948 plus minus 5 and 907 plus minus 5 ma assuming that this terrane cooled slowly following high grade metamorphism and that the samples have experienced the same thermal history the difference in dates apparently reflects a corresponding difference in blocking temperature for diffusion of radiogenic argon in these hornblende samples the fe fe mg mn of the hornblende samples are 0 8 and 0 6 the higher ratio corresponding to the younger sup 40 ar sup 39 ar sub k date transmission electron microscopy observations indicate that both hornblende samples are homogeneous and devoid of any exsolution but contain zones of fibrous phyllosilicates approximately 0 1 to 2 mu m wide parallelling 100 and 110 these alteration zones probably formed during post metamorphic cooling as a result of the migration of fluids through the hornblendes and are obvious pathways for argon escape from hornblende as these features are more abundant in the hornblende sample with the younger sup 40 ar sup 39 ar date and higher fe fe mg mn they may influence the argon blocking temperature by effectively partitioning the hornblende grains intomore diffusion domains of varying size biotite from the granitic gneiss yields an sup 40 ar sup 39 ar sub k date of 853 plus minus 2 ma with a mildly discordant step heating spectrum that in part reflects the degassing of submicroscopic inclusions precipitated during alteration of the host biotite plagioclase from the amphibolite yields a sup 40 ar sup 39 ar sub k integrated date of 734 plus minus 3 ma less

isotopic u pb ages of zircon and monazite from the leinster granite southeast ireland a more precise age for the synkinematic emplacement of the large s type leinster batholith southeast ireland has been obtained by u pb dating of zircon and monazite separates from the two main granite varieties of the northern pluton a concordant age of 405 2 ma derived from monazite is considered to reflect both the age of intrusion and the main regional deformation event d1 in southeast ireland the monazite age is in good agreement with an earlier less precise whole rock rb sr isochron determination the zircon data indicate recent pb loss effects and the existence of a small component of inherited radiogenic pb derived from a crustal precursor during the generation of the batholith

cryptic sr and nd isotopic variation across the leinster granite southeast ireland rb sr isotope whole rock data from the end caledonian leinster batholith define an errorchron age of 464 26 ma appreciably older than the accepted emplacement age of c 405 ma this anomalously old age is the consequence of a highly variable initial sr isotopic composition initial nd ratios and t dm model ages also show a wide range of values however these isotopic variations are neither randomly distributed nor related to petrographic changes but instead reflect in a simple way geographic position about the axis of the batholith the isotopic pattern revealed in the leinster batholith means that isochron ages obtained from s type granites may be largely dependent on the sampling scheme adopted the variable isotopic composition of the granite most likely resulted from either a heterogeneous metasedimentary source or hybridization of coeval dominantly crustal melts

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

plate boundary deformation associated with the great sumatra andaman earthquake the sumatra andaman earthquake of 26 december 2004 is the first giant earthquake moment magnitude m w 9 0 to have occurred since the advent of modern space based geodesy and broadband seismology it therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events here we report estimates of the ground displacement associated with this event using near field global positioning system gps surveys in northwestern sumatra combined with in situ and remote observations of the vertical motion of coral reefs these data show that the earthquake was generated by rupture of the sunda subduction megathrust over a distance of 1 500 kilometres and a width of 150 kilometres megathrust slip exceeded 20 metres offshore northern sumatra mostly at depths shallower than 30 kilometres comparison of the geodetically and seismically inferred slip distribution indicates that 30 per cent additional fault slip accrued in the 1 5 months following the 500 second long seismic rupture both seismic and aseismic slip before our re occupation of gps sites occurred on the shallow portion of the megathrust where the large aceh tsunami originated slip tapers off abruptly along strike beneath simeulue island at the southeastern edge of the rupture where the earthquake nucleated and where an m w 7 2 earthquake occurred in late 2002 this edge also abuts the northern limit of slip in the 28 march 2005 m w 8 7 nias simeulue earthquake

osl dating and gpr mapping of palaeotsunami inundation a 4000 year history of indian ocean tsunamis as recorded in sri lanka to evaluate and mitigate tsunami hazard as long as possible records of inundations and dates of past events are needed coastal sediments deposited by tsunamis tsunamites can potentially provide this information however of the three key elements needed for reconstruction of palaeotsunamis identification of sediments dating and finding the inundation distance the latter remains the most difficult the existing methods for estimating the extent of a palaeotsunami inundation rely on extensive excavation which is not always possible here by analysing tsunamites from sri lanka identified using sedimentological and paleontological characteristics we show that their internal dielectric properties differ significantly from surrounding sediments the significant difference in the value of dielectric constant of the otherwise almost indistinguishable sediments is due to higher water content of tsunamites the contrasts were found to be sharp and not to erode over thousands of years they cause sizeable electromagnetic wave reflections from tsunamite sediments which permit the use of ground penetrating radar gpr to trace their extent and morphology in this study of the 2004 boxing day indian ocean tsunami we use gpr in two locations in sri lanka to trace four identified major palaeotsunami deposits for at least 400 m inland investigation inland was constrained by inaccessible security zones the subsurface extent of tsunamites not available without extensive excavation provides a good proxy for inundation the deposits were dated using the established method of optically stimulated luminescence osl this dating partly corroborated by available historical records and independent studies contributes to the global picture of tsunami hazard in the indian ocean the proposed method of combined gpr osl based reconstruction of palaeotsunami deposits enables estimates of inundation recurrence and therefore tsunami hazard for any sandy coast with identifiable tsunamite deposits the method could be also used for anchoring and synchronizing chronologies of ancient civilisations adjacent to the ocean shores

holocene sea levels along the andaman sea coast of thailand for the malay thai peninsula several sea level curves for the younger holocene based on field evidence as well as on hydro isostatic modelling of a far field site have been published the general assumption is a rapid rise to a mid holocene maximum up to 5 m above present sea level followed by a constant or oscillating regression however from the andaman sea coast of thailand which was affected by the 2004 tsunami only isolated observations are available regarding holocene sea levels thus the timing and magnitude of the holocene highstand as well as the course of the regression remain to be defined as several palaeotsunamis could be detected in the meantime it is important to know the related sea levels as exactly as possible to judge the energy inundation width and potential wave height of these events therefore fixed biological indicators from the rocky coasts of the phang nga bay and phuket as well as morphological indicators from beach ridge and swale sequences along the exposed west coast ko phra thong were studied to gain information about the holocene sea level development in this region while oyster and coral data from the phang nga bay and phuket document a holocene maximum of 2 6 m at 5700 cal bp the ridge crests and swale bases in the northwest of the study area point to maximum heights of 1 5 2 0 m above the present level around 5300 years ago during the last 3000 years to when the largest part of the holocene palaeotsunami deposits from thailand was dated relative sea levels rsl in both areas did not exceed 1 5 m

depositional facies and sedimentary successions of earthquake induced tsunami deposits in upper pleistocene incised valley fills central japan abstract two anomalous deposits with well preserved sedimentary structures were discovered in a drowned valley and in relict barrier sand body deposits in the furuya mud and kyomatsubara sand of the upper pleistocene incised valley fills the sedimentary features of both deposits are interpreted as earthquake induced tsunami deposits which were deposited in incised valley fills the tsunami deposit in the drowned valley furuya mud is 150 cm thick and shows a contorted structured bed in the lower part and cross laminated sand in the upper part the tsunami deposit in barrier sand body kyomatsubara sand is 270 cm thick and shows structureless sand with mud clasts in the lower part cross laminated sand with mud drapes in the middle part and mud with small wave ripples in the upper part taken together these sedimentary features suggest a model for the composite succession which is comprised of three units a lower earthquake shock influenced anomalous convoluted part a middle part dominated by tsunami generated tractional currents and an upper suspended sediment part the lower part is interpreted as earthquake event deposits seismites and the middle and upper parts as tsunami current deposits tsunamiites

assembly of proterozoic australia implications of a revised pole for the 1070 ma alcurra dyke swarm central australia summary the pole position for the late mesoproterozoic alcurra formerly kulgera dyke swarm ads musgrave block central australia has been revised by adding new data from two more dykes a palaeomagnetic fold test is positive at the 99 percent confidence level and the pole position is latitude 2 8 s longitude 80 4 e dp 7 2 dm 10 7 new 40ar 39ar determinations on single biotite grains from country rock gneiss 20 cm from the contact with an alcurra dyke yield ages from 1068 2 ma to 1085 2 ma 2 in addition 40ar 39ar determinations on two samples of aggregates of very fine grained biotite from the mesostasis of a stuart dyke sd arunta inlier northern territory yield ages of 1059 2 and 1066 3 ma 2 these new ages are in agreement with those of the 1070 ma warakurna large igneous province west central australia indicating that both the ads and sd belong to that suite palaeomagnetic poles determined by others for the ads and sd are indistinguishable from each other but cannot be presently combined as a single pole because the published information on the sd is incomplete an analysis of the palaeogeography implied by the dispersed palaeomagnetic poles from members of the extended warakurna suite shows that the present relationships between the major precambrian cratons west north and south australian which constitute australia west of the tasman line are inconsistent with the inferred relationship at 1070 ma nor is it apparent that internal deformations within the separate cratons are the cause of the dispersion our findings imply that these major australian cratons must have finally assembled sometime after 1070 ma

petrogenesis of the granitic donkerhuk batholith in the damara belt of namibia protracted syntectonic short range crustal magma transfer the areally extensive 5000 km2 syn tectonic ca 520 ma mainly s type donkerhuk batholith was constructed through injection of thousands of mainly sheet like magma pulses over 20 25 myr it intruded schists of the southern zone accretionary prism in the damara belt of namibia each magma pulse had at least partly crystallised prior to the arrival of the following batch however much of the batholith may have remained partially molten for long periods close to the h2o saturated granite solidus the batholith shows extreme variation in chemistry while having limited mineralogical variation and seems to be the world s most heterogeneous granitic mass the nd model ages of 2 ga suggest that eburnean rocks of the former magmatic arc structurally overlain by the accretionary wedge are the most probable magma sources crustal melting was initiated by mantle heat flux probably introduced by thermal diffusion rather than magma advection the granitic magmas were transferred from source to sink with minimal intermediate storage the whole process having occurred in the middle crust resulting in feeble crustal differentiation despite the huge volume of silicic magma generated source heterogeneity controlled variation in the magmas and neither mixing nor fractionation was prominent however due to the transpressional emplacement regime local filter pressing formed highly silicic liquids as well as felsic cumulate rocks the case of the donkerhuk batholith demonstrates that emplacement level tectonics can significantly influence compositional evolution of very large syn tectonic magma bodies

tracking the rupture of the mw 9 3 sumatra earthquake over 1 150 km at teleseismic distance on 26 december 2004 a moment magnitude mw 9 3 earthquake occurred along northern sumatra the nicobar and andaman islands resulting in a devastating tsunami in the indian ocean region the rapid and accurate estimation of the rupture length and direction of such tsunami generating earthquakes is crucial for constraining both tsunami wave height models as well as the seismic moment of the events compressional seismic waves generated at the hypocentre of the sumatra earthquake arrived after about 12 min at the broadband seismic stations of the german regional seismic network grsn located approximately 9 000 km from the event here we present a modification of a standard array seismological approach and show that it is possible to track the propagating rupture front of the sumatra earthquake over a total rupture length of 1 150 km we estimate the average rupture speed to be 2 3 2 7 km s 1 and the total duration of rupture to be at least 430 s and probably between 480 and 500 s

melting of a subduction modified continental lithospheric mantle evidence from late proterozoic mafic dike swarms in central australia geochemical and nd isotopic studies of two postorogenic late proterozoic 1083 23 ma high mg tholeiitec dike swarms in central australia indicate that the dike swarms were derived by partial melting of the continental lithospheric mantle which was modified by subduction processes during major crust formation events in the region both dike swarms stuart and kulgera which intrude the arunta and musgrave inliers respectively resemble island arc tholeiites in terms of geochemical features they yield whole rock sm nd ages of 1853 189 ma with nd 4 2 4 2 stuart and 1589 165 ma with nd 1 7 3 6 kulgera the two whole rock ages and initial nd values are remarkably similar to the oldest u pb zircon ages and initial nd values obtained from the corresponding basement blocks these isotopic data are interpreted as recording sm nd fractionation events in the continental lithospheric mantle associated with major episodes of crust formation in the early proterozoic

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

multi proxy records of regionally sourced tsunamis new zealand abstract a multi proxy study of sediment cores from kaituna bay mimiwhangata in northern new zealand has produced a record of three palaeotsunamis dated to around 6500 cal yr bp 2800 cal yr bp and 1450 ad these events punctuate a coastal palaeoenvironmental history spanning the last 8000 years or more in which the site progressed from a semi open lagoon to a freshwater swamp proxies used included stratigraphy geochemistry palynology diatoms foraminifera geomorphology and a regional palaeotsunami synthesis the identification of tsunamigenic sources for these events is tentative we propose that the two oldest events are associated with a source in the tonga kermadec trench region with the most recent possibly associated with the kuwae caldera collapse in 1452 1453 ad palaeotsunami deposits contemporaneous with the estimated age of the three events identified in this study were used to assist in identifying possible source regions the development of regional and national palaeotsunami databases is in its infancy but as more data become available the ability to determine the source magnitude and frequency of past events will improve this will greatly enhance our understanding of the regional risk from tsunamis

holocene hydrological events and human induced environmental changes reflected in a southeastern mediterranean fluvial archive abstract the chronostratigraphy of an eastern mediterranean holocene fluvial sequence reflects global trends climate and sea level local modulations hydrological regime and storm surges and anthropogenic impact two continuous cores retrieved from the tanninim stream estuary on the carmel coast of israel are dated by optically stimulated luminescence osl to span the holocene the sedimentology and faunal assemblages are analyzed for reconstructing environmental conditions despite time gaps recognized in the fluvial successions three main depositional periods provide distinctive archives capturing natural and anthropogenic centennial to millennial changes alternations between enhanced and reduced fluvial activity associated with humid and dry climate conditions characterized the early to mid holocene fluvial record between about 7 8 and 5 7 ka and may match eastern mediterranean climate records the first humid phase from 8 to 6 ka features organic rich fine sediments and proliferating brackish ostracods foraminifera and molluscs the appearance of this biofacies indicates the initiation of seepage from the yarkon tanninim aquifer through the brackish oligohaline enot timsah springs the advancing coastline due to sea level rise starting about 5 8 ka resulted in an increasing supply of quartz sands and marine transported foraminifera relatively fast accumulation of organic rich fine grained sediments with enhanced preservation of brackish fauna during the late holocene is probably associated with maintenance of the tanninim dams during the early arab period 7th 8th centuries ce the last century has been characterized by accelerated sedimentation rates that may be associated with reduced vegetation cover due to modern human activity and by deposition by a high energy surge event this study demonstrates that the lower part of a semi arid southeastern mediterranean estuary responds to periods of climatic and sea level change on a regional scale and to human impact and abrupt past hydrological events on a local scale

microtextural analysis of quartz grains of tsunami and non tsunami deposits a case study from tirua chile abstract in order to estimate the tsunami hazard it is essential to reliably identify and differentiate tsunami deposits from other high energy events like storms recently the microtextural analysis of quartz grain surfaces was introduced as a method to differentiate between tsunami and other deposits using tsunami deposits sampled from a bank profile of the tirua river central chile an area that was significantly affected by the 2010 and 1960 chile tsunamis we tested the microtextural analysis method for its capability to identify tsunami deposits a total of 815 quartz grain surfaces of two tsunami layers two non tsunami marsh sediment samples and three reference samples from nearby beach dune and river were analyzed using scanning electron microscopy sem we grouped the detected microtexture features into five microtextural families angularity fresh surfaces percussion marks adhering particles and dissolution features both the tsunami deposits and reference samples reveal high numbers of fresh surfaces and percussion marks thus there are no statistically significant differences between tsunami beach dune and river deposits in characteristics and abundances in all microtextural families our study indicates that the microtextural analysis of quartz grains may not be a suitable method to identify tsunami deposits in tirua chile due to local factors such as high numbers of inherited microtextures and the possible effects of the high amount of heavy minerals

palaeomagnetism of the ejecta bearing bunyeroo formation late neoproterozoic adelaide fold belt and the age of the acraman impact abstract a new palaeomagnetic study has been conducted on haematitic shales and siltstones of the late neoproterozoic bunyeroo formation in the adelaide fold belt geosyncline south australia which host an extensive horizon of shock deformed rock fragments and microtektite like material of probable impact origin thermal step demagnetisation of 116 samples of red shale and siltstone from six sections sites revealed a high temperature component with a bedding corrected site mean direction of remanence of d 56 6 i 29 3 95 10 7 that gives a pole at 18 1 s 16 3 e dp 6 5 dm 11 8 the high temperature component provides a positive tectonic fold test 99 level of confidence the bunyeroo high temperature remanence direction is near the remanence direction d 50 i 40 indicated by modelling the subsurface magnetic source of the central high amplitude anomaly at acraman australia s largest confirmed meteorite impact structure 220 350 km west of the adelaide fold belt and also is close to the mean direction d 48 3 i 54 7 95 5 2 determined for surface melt rock from acraman statistical tests show that the virtual geomagnetic poles indicated by the directions for the subsurface central magnetic source and surface melt rock at acraman may be regarded as subsets of the bunyeroo palaeomagnetic pole position indicating that the three pole positions are statistically indistinguishable the results imply that the subsurface magnetic source and surface melt rock acquired their remanence in the ambient geomagnetic field during cooling after the impact when structural disturbance had ceased while the bunyeroo formation was accumulating the agreement among the various remanence directions argues strongly that the ejecta horizon in the bunyeroo formation was derived from acraman the present findings confirm that the acraman impact occurred in the late neoproterozoic about 590 ma which is the age of the bunyeroo formation provided by rb sr whole rock shale dating of equivalent and contiguous strata in the adelaide fold belt region the bunyeroo palaeomagnetic data give a palaeolatitude of 15 indicating a low palaeolatitude for the acraman impact and supporting other findings that the adelaide fold belt occupied low to equatorial palaeolatitudes during the late neoproterozoic