marine isotope stage 4 in australasia a full glacial culminating 65 000 years ago global connections and implications for human dispersal patrickde deckker lee j arnold sandervan der kaars germain bayone jan berend w stuut kerstin perner raquel lopes dos santos ryu uemura martina demuro

hydroclimatic interpretation of quaternary shorelines on south australian playas abstract the catchment of lake eyre is one of the world s largest internally drained basins the playas near its depocentre the driest region of australia contain a partial record of quaternary climatic and hydrologic events for the last full glacial cycle and probably beyond ancient beach ridges marginal to lakes eyre frome callabonna and blanche have been dated using thermoluminescence tl to provide evidence for major changes in the hydrological regime of the basin beach ridges around lake eyre provide evidence of high lake stands up to 27 m above the present lake floor during what probably corresponds to the middle to latter part of marine oxygen isotope stage 5 there is evidence also for even higher lake stands associated with earlier isotope stages three tl dates identify a period of aeolian activity during stage 4 and a further 5 tl dates from lakes eyre and frome indicate that high lake stands occurred between about 55 and 40 ka corresponding with stage 3 the stage 5 and stage 3 high stands both relate to periods of enhanced fluvial activity previously identified in the lake eyre basin and elsewhere in australia in contradiction with other work a few tl dates from some playas suggest a possible major episode of high lake levels immediately preceding or at the start of the last glacial maximum lgm 26 22 ka this may relate to a sharp temperature suppression and an increase in runoff by rivers fed from monsoons in the north while a set of relatively low elevation late holocene beaches have been dated on two of the playas a period of enhanced precipitation and stream flow in the early to mid holocene appears not to have formed higher beaches possibly due to high temperatures and evaporation rates at that time the filling of lake eyre during and since stage 5 appears to have been to no more than to a level of 12 m australian height datum ahd possibly due a spillway at about this elevation in the form of the warrawoocara channel connecting lake eyre with playas to the southeast lakes gregory blanche callabonna and frome such overflows from one large basin to another would have had a major impact on the hydrology of the region in addition to enhanced runoff essential for the maintenance of high lake levels must have been local temperatures and evaporation rates significantly reduced from present day levels

late quaternary productivity changes from offshore southeastern australia a biomarker approach reconstructions of primary productivity at low latitudes have been the focus of several studies to better understand how the export of nutrient rich intermediate southern ocean so waters influences productivity at these latitudes this was triggered by the general observation of minima in the planktonic foraminiferal delta c 13 values during deglaciations which was interpreted as an isotopic signal of intermediate so waters together with a concomitant increase in diatom productivity at some equatorial sites however the impact of these so waters on productivity at higher latitudes is not well constrained here we compare a high resolution planktonic foraminiferal delta c 13 record with total organic carbon and biomarker records for proboscia diatoms and haptophytes in marine sediments from offshore southeastern australia the planktonic foraminiferal delta c 13 record shows distinct minima during deglaciations and the marine isotope stage 4 3 transition tentatively suggesting that c 13 depleted so waters reached the coast of southeastern australia however it did not result in increased productivity during these periods instead the highest primary productivity period as indicated by total organic carbon and alkenone accumulation rates occurred during the last glacial maximum while proboscia diatoms mainly proliferated during interglacials and marine isotope stage 3 matching periods of increased diatom productivity in some sites of the eastern equatorial pacific our study suggests that increased primary productivity offshore southeastern australia was mainly due to stronger westerly winds during glacial periods while proboscia diatom productivity was probably controlled by the transport of silicic acid to this area

hydrological transformation coincided with megafaunal extinction in central australia central to the debate over the extinction of many of australia s last surviving megafauna is the question was climate changing significantly when humans arrived and megafauna went extinct here we present a new perspective on variations in climate and water resources over the last glacial cycle in arid australia based on the study of the continent s largest lake basin and its tributaries by dating paleoshorelines and river deposits in the lake eyre basin we show that major hydrological change caused previously overflowing megalakes to enter a final and catastrophic drying phase at 48 2 ka just as the giant bird genyornis newtoni went extinct 50 45 ka the disappearance of genyornis and other megafauna has been previously attributed to ecosystem collapse coincident with the spread of fire wielding humans our findings suggest a climate driven hydrological transformation in the critical window of human arrival and megafaunal extinction and the results call for a re evaluation of a humanmediated cause for such extinctions in arid australia

a 60 000 year record of environmental change for the wet tropics of north eastern australia based on the odp 820 marine core palynomorphs from the odp site 820 marine core have provided a detailed record of terrestrial environmental responses to glacial interglacial forcing over the last 250 000 years in the australian wet tropics the development of an accurate geochronological framework for this key sequence has proved challenging consequently different dominant forcing mechanism s have been proposed to drive environmental change in the low latitudes a new chronology for the last 60 000 years based on accelerator mass spectrometry radiocarbon c dates of pollen concentrate material and the existing marine isotope stage boundaries mis 4 to 1 has been produced this new chronology provides a robust geochronological framework for interpreting environmental records across the region in particular our age model helps to resolve several debates concerning the timing of climatic changes and their impacts on both the marine and the terrestrial systems as well as possible human arrival and associated impacts on the region s ecosystems our findings suggest c dating of terrestrial pollen concentrate in marine sediments is a valuable tool for resolving major chronological uncertainties in potentially diagenetically altered marine caco sediments and should play a role in future multi dating strategies copyright

anisotropic velocity tomography a case study in a near surface rock mass cross borehole data were acquired in the surface crown pillar of a massive sulfide ore mine the data consist of five two dimensional 2 d cross borehole panels each with approximately 900 source receiver pairs the panels were located within the crown pillar at either side of and within a major subvertical fault zone that intersects the orebody an initial analysis of the data indicates that the bedrock containing the orebody is seismically anisotropic a rigorous analysis of the traveltimes using anisotropic velocity tomography confirms the initial assessment that anisotropy exists within the crown pillar rock mass anisotropic velocity tomography is the generalization of tomographic methods to anisotropic media as in any geophysical problem the data are insufficient to completely resolve the distributions of the rock properties at all scale lengths we use external constraints on the roughness of the final solution to ensure an algebraically well posed problem plots of the data residuals the t

the cause of carbon isotope minimum events on glacial terminations the occurrence of carbon isotope minima at the beginning of glacial terminations is a common feature of planktic foraminifera carbon isotopic records from the indo pacific sub antarctic and south atlantic we use the 13 c record of a thermocline dwelling foraminifera neogloboquadrina dutertrei and surface temperature estimates from the eastern equatorial pacific to demonstrate that the onset of 13 c minimum events and the initiation of southern ocean warming occurred simultaneously timing agreement between the marine record and the 13 c minimum in an antarctic atmospheric record suggests that the deglacial events were a response to the breakdown of surface water stratification renewed circumpolar deep water upwelling and advection of low 13 c waters to the convergence zone at the sub antarctic front on the basis of age agreement between the absolute 13 c minimum in surface records and the shift from low to high 13 c in the deep south atlantic we suggest that the 13 c rise that marks the end of the carbon isotope minima was due to the resumption of north atlantic deep water influence in the southern ocean

weighted least squares criteria for seismic traveltime tomography methods are developed for design of linear tomographic reconstruction algorithms with specified properties assuming a starting model with constant slowness an algorithm with the following properties is found 1 the optimum constant for the starting model is determined automatically 2 the weighted least squares error between the predicted and measured traveltime data is as small as possible 3 the variance of the reconstructed slowness from the starting model is minimized 4 rays with the greatest length have the least influence on the reconstructed slowness and 5 cells with most ray coverage tend to deviate least from the background value the resulting algorithm maps the reconstruction problem into a vector space where the contribution to the inversion from the background slowness remains invariant while the optimum contribution in orthogonal directions are found for a starting model with constant slowness the reconstruction algorithm has analogous properties

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

an efficient sequential strategy for realizing cross gradient joint inversion method and its application to 2 d cross borehole seismic traveltime and dc resistivity tomography

diatom productivity in the equatorial pacific ocean from the last glacial period to the present a test of the silicic acid leakage hypothesis 1 the silicic acid leakage hypothesis salh suggests that during glacial periods unused silicic acid escaped the southern ocean into the equatorial oceans causing an ecological shift favoring diatoms relative to coccolithophorids and a drawdown of co2 the 230th normalized opal fluxes and 231pa 230th ratios were measured in eleven equatorial pacific cores to reconstruct diatom productivity over the past 30 kyr and to test the salh holocene spatial patterns of opal flux are strongly correlated with 231pa 230th ratios and with satellite estimates of primary productivity down core opal flux records do not support the salh but show holocene opal burial to exceed that of the late glacial period by 35 or 2 8 gt opal kyr across the equatorial pacific this suggests that the salh may not account for lower atmospheric co2 levels during the late glacial however the data do support results from previous studies that invoke increased el nino like conditions during this time

revisiting the late pleistocene mammal extinction record at tight entrance cave southwestern australia tight entrance cave tec in southwestern australia provides a pleistocene sequence documenting the extinction of 14 large mammal species this record has been interpreted as indicating that extinctions did not occur during or before the penultimate glacial maximum pgm and that humans played a primary role in the extinctions however it remains possible that the majority of extinct megafauna persisted no later than the pgm the tec extinctions correspond with vegetation change a cooling drying trend increased biomass burning and increasingly unstable small mammal communities the initiation of these trends predates human arrival on the continent and implies environmentally mediated extinctions

sediment mixing at nonda rock investigations of stratigraphic integrity at an early archaeological site in northern australia and implications for the human colonisation of the continent archaeological excavations in sediments dating to between 60 000 and 40 000 years ago are rare in australia yet this is precisely the period in which most archaeologists consider that aboriginal people arrived on the continent in the few cases where such early sites have been investigated questions have invariably been raised as to the reliability of stratigraphic associations between cultural items and the surrounding sediments this paper describes a method for examining sediment mixing in a stratigraphic sequence using the optically stimulated luminescence osl signals from individual sand sized grains of quartz we apply this method to the archaeological site of nonda rock north queensland in combination with radiocarbon dating of charcoal fragments to construct chronologies for human occupation and for the preceding culturally sterile deposits our age estimates have implications for the timing of first human arrival in australia

wet phases in the sahara sahel region and human migration patterns in north africa the carbon isotopic composition of individual plant leaf waxes a proxy for c3 vs c4 vegetation in a marine sediment core collected from beneath the plume of sahara derived dust in northwest africa reveals three periods during the past 192 000 years when the central sahara sahel contained c3 plants likely trees indicating substantially wetter conditions than at present our data suggest that variability in the strength of atlantic meridional overturning circulation amoc is a main control on vegetation distribution in central north africa and we note expansions of c3 vegetation during the african humid period early holocene and within marine isotope stage mis 3 50 45 ka and mis 5 120 110 ka the wet periods within mis 3 and 5 coincide with major human migration events out of sub saharan africa our results thus suggest that changes in amoc influenced north african climate and at times contributed to amenable conditions in the central sahara sahel allowing humans to cross this otherwise inhospitable region

a new species of zangerlia testudines nanhsiungchelyidae from the upper cretaceous redbeds at bayan mandahu inner mongolia and the relationships of the genus zangerlia neimongolensis sp nov is described on the basis of material from the upper cretaceous redbeds at bayan mandahu in inner mongolia zangerlia neimongolensis is similar to zangerlia testudinimorpha in the proportions of the carapace and plastron and presence of a knob at the posterior end of the neural series but differs from it in the arrangement of scutes covering the bridge the placement of zangerlia in the nanhsiungchelyidae is supported by derived features of the bridge peripherals and plastral scutes shared by z neimongolensis basilemys and nanhsiungchelys these are the presence of ventrally expanded sixth inframarginal scutes humeral scutes that are narrow at the midline and expanded laterally pectoral scutes that are wide at the midline and narrow laterally and large rectangular abdominal scutes the skull of zangerlia is more primitive than that of nanhsiungchelys the only other member of the family for which a skull is known it shows extensive emargination of the temporal and

new psittacosaur occurrences in inner mongolia psittacosaur materials were collected from seven localities in the course of dinosaur project fieldwork in inner mongolia two new species of psittacosaurus are recognized bringing the number of well defined species to six one based on a nearly complete skeleton resembles psittacosaurus mongoliensis but is a smaller animal with a relatively larger head and longer tail the other species possesses jugal horns but exhibits a different combination of characters than psittacosaurus sinensis and psittacosaurus xinjiangensis a larger matrix of taxa and characters than is presently available will be necessary to resolve adequately phylogenetic relationships within the genus psittacosaurs were small dinosaurs the skeletons of which are preserved in unusual completeness in proximity to aeolian environments of deposition their small brain size relative to that of modern mammals of similar body size implies a relatively restricted behavioral repertoire

a novel method for the rapid analysis of levoglucosan in soils and sediments abstract we have developed a novel method based on high performance liquid chromatography mass spectrometry for the rapid and quantitative analysis of levoglucosan in geological samples compared with existing methods it does not require derivatization or extensive work up and requires less sample material its validity is demonstrated by way of application to soil samples collected from a burned dune area and a late quaternary marine sediment

crosshole seismic tomography with cross firing geometry abstractwe have developed a case study of crosshole seismic tomography with a cross firing geometry in which seismic sources were placed in two vertical boreholes alternatingly and receiver arrays were placed in another vertical borehole there are two crosshole seismic data sets in a conventional sense these two data sets are used jointly in seismic tomography because the local sediment is dominated by periodic flat thin layers there is seismic anisotropy with different velocities in the vertical and horizontal directions the vertical transverse isotropy anisotropic effect is taken into account in inversion processing which consists of three stages in sequence first isotropic traveltime tomography is used for estimating the maximum horizontal velocity then anisotropic traveltime tomography is used to invert for the anisotropic parameter which is the normalized difference between the maximum horizontal velocity and the maximum vertical velocity finally anisotropic waveform tomography is impl

the late quaternary decline and extinction of palms on oceanic pacific islands late quaternary palaeoecological records of palm decline extirpation and extinction are explored from the oceanic islands of the pacific ocean despite the severe reduction of faunal diversity coincidental with human colonisation of these previously uninhabited oceanic islands relatively few plant extinctions have been recorded at low taxonomic levels recent faunal extinctions on oceanic islands are concentrated in larger bodied representatives of certain genera and families fossil and historic records of plant extinction show a similar trend with high representation of the palm family arecaceae late holocene decline of palm pollen types is demonstrated from most islands where there are palaeoecological records including the cook islands fiji french polynesia the hawaiian islands the juan fernandez islands and rapanui a strong correspondence between human impact and palm decline is measured from palynological proxies including increased concentrations of charcoal particles and pollen from cultivated plants and invasive weeds late holocene extinctions or extirpations are recorded across all five of the arecaceae subfamilies of the oceanic pacific islands these are most common for the genus pritchardia but also many sedis fossil palm types were recorded representing groups lacking diagnostic morphological characters

silicic acid leakage from the southern ocean a possible explanation for glacial atmospheric pco2 1 using a simple box model we investigate the effects of a reduced si n uptake ratio by antarctic phytoplankton on the marine silica cycle and atmospheric pco2 recent incubation experiments demonstrate such a phenomenon in diatoms when iron is added hutchins and bruland 1998 takeda 1998 franck et al 2000 the southern ocean may have supported diatoms with reduced si n uptake ratios compared to today during the dustier glacial times petit et al 1999 a similar reduction in the uptake ratio may be realized with an increased production of nondiatom phytoplankton such as phaeocystis our model shows that reduced si n export ratios in the southern ocean create excess silicic acid which may then be leaked out to lower latitudes any significant consumption of the excess silicic acid by diatoms that leads to an enhancement in their growth at the expense of coccolithophorids diminishes caco3 production and therefore diminishes the carbonate pump in our box model the combination of a reduced carbonate pump and an open system carbonate compensation draw down steady state atmospheric co2 from the interglacial 277 to 230 242 ppm depending on where the excess silicic acid is consumed by comparison the atmospheric pco2 sensitivity of general circulation models to carbonate pump forcing is 3 5 fold greater which combined with carbonate compensation can account for peak glacial atmospheric pco2 we discuss the importance of the initial rain ratio of caco3 to organic carbon on atmospheric pco2 and relevant sedimentary records that support and constrain this silicic acid leakage scenario

new u th ages for pleistocene megafauna deposits of southeastern queensland australia arguments over the extinction of pleistocene megafauna have become particularly polarised in recent years causes for the extinctions are widely debated with climate change human hunting and or habitat modification or a combination of those factors being the dominant hypotheses however a lack of a spatially constrained chronology for many megafauna renders most hypotheses difficult to test here we present several new u th dates for a series of previously undated megafauna bearing localities from southeastern queensland australia the sites were previously used to argue for or against various megafauna extinction hypotheses and are the type localities for two now extinct pleistocene marsupials including the giant koala phascolarctos stirtoni the new dating allows the deposits to be placed in a spatially and temporally constrained context relevant to the understanding of australian megafaunal extinctions the results indicate that the joint texas caves megafaunal assemblage is middle pleistocene or older 292 ky the cement mills gore megafaunal assemblage is late pleistocene or older 53 ky and the russenden cave bone chamber texas caves megafaunal assemblage is late pleistocene 55 ky importantly the new results broadly show that the sites date prior to the hypothesised megafaunal extinction window i e 30 50 ky and therefore cannot be used to argue exclusively for or against human climate change extinction models without first exploring their palaeoecological significance on wider temporal and spatial scales

basilochelys macrobios n gen and n sp a large cryptodiran turtle from the phu kradung formation latest jurassic earliest cretaceous of the khorat plateau ne thailand

tetrapod track assemblages from lower cretaceous desert facies in the ordos basin shaanxi province china and their implications for mesozoic paleoecology tetrapod ichnofaunas are reported from desert playa lake facies in the lower cretaceous luohe formation at baodaoshili shaanxi province china which represent the first asian example of an ichnnofauna typical of the chelichnus ichnofacies brasilichnium sub ichnofacies characteristic of desert habitats the mammaliomorph tracks assigned to brasilichnium represent the first report of this ichnogenus from asia the assemblages also contain three different theropod trackway morphotypes one very wide magnoavipes like morphotype one relatively wide broad toed small eubrontes like form with short steps and strides and wide straddle and an elongate morphotype sarmientichnus with longer steps and narrower straddle representing a didactyl trackmaker the latter being the first example of the enigmatic ichnogenus found outside its type area in argentina the sarmientichnus occurrence the first in asia has important implications demonstrating that the trackmaker was not monodactyl but didactyl with probable affinities to deinonychosaurians which are ichnologically well represented in the lower cretaceous of asia although morphologically distinctive sarmientichnus should be recognized as a form ichnotaxon compromised by suboptimal preservation the combination of brasilichnium isp sarmientichnus isp and tridactyl theropod tracks indicates mammaliomoprhs and small theropods and is comparable to ichnofaunas from similar desert facies on other continents thus cretaceous desert ichnofaunas from china are consistent with global ichnofacies predictions

re evaluating the late quaternary fossil mammal assemblage of seton rockshelter kangaroo island south australia including the evidence for late surviving megafauna it is widely accepted that most larger australian vertebrates were extinct by 40 ka the reliability of 20 ka radiocarbon 14c ages on charcoal stratigraphically associated with sthenurine short faced kangaroo tooth fragments from seton rockshelter kangaroo island have therefore proven contentious some researchers have argued these fossils were in situ while others have claimed they were reworked to address this we obtained new 14c ages on bones from the site these bone ages are not only consistent with earlier charcoal ages but are in near perfect stratigraphic order providing strong support for the site s stratigraphic integrity our analyses indicate units aged 21 17 ka were primarily accumulated by tasmanian devils sarcophilus harrisii and owls tyto species after which humans became the primary accumulation agent the tight chronology faunal trends and current lack of evidence for older layers from which specimens could have been reworked suggest the sthenurine remains may be in situ however because attempts to directly date sthenurine material failed we cannot confidently assert that they survived to this time therefore seton rockshelter may be best excluded from the pleistocene extinction debate until the site can be re excavated and more conclusive evidence collected including more complete or directly datable sthenurine remains copyright 2015 john wiley sons ltd

multiscale imaging of complex structures from multifold wide aperture seismic data by frequency domain full waveform tomography application to a thrust belt summary an application of full waveform tomography to dense onshore wide aperture seismic data recorded in a complex geological setting thrust belt is presented the waveform modelling and tomography are implemented in the frequency domain the modelling part is solved with a finite difference method applied to the visco acoustic wave equation the inversion is based on a local gradient method only the p wave velocity is involved in the inversion the inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies this defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images the linearized waveform tomography requires an accurate starting velocity model that has been developed by first arrival traveltime tomography after specific pre processing of the data 16 frequency components ranging between 5 4 and 20 hz were inverted ten iterations were computed per frequency component leading to 160 tomographic models the waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high resistivity bodies the relevance of the tomographic images is locally demonstrated by comparison of a velocity depth function extracted from the waveform tomography models with a coincident vertical seismic profiling vsp log available on the profile moreover comparison between observed and synthetic seismograms computed in the starting traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide angle reflections from southwest dipping geological structures this study demonstrates that the combination of first arrival traveltime and frequency domain full waveform tomographies applied to dense wide aperture seismic data is a promising approach to quantitative imaging of complex geological structures indeed wide aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography this is critical because the building of the macromodel remains an open question when only near vertical reflection data are considered

the parabasisphenoid complex in mesozoic turtles and the evolution of the testudinate basicranium during the early development of turtles and other amniotes the parabasisphenoid or basisphenoid s l is formed by at least two centers of ossification the endochondral basisphenoid s s and the dermal parasphenoid this fusion is usually so dramatic that the two elements cannot be distinguished from each other in the adult stage here we describe the basicranium of two species of mesozoic turtles from europe plesiochelys etalloni and pleurosternon bullockii partly using micro ct computer tomography scans and show that in both taxa para and basisphenoid remain distinguishable throughout life we also identify the extent that each of the two elements has contributed to the formation of the braincase floor because the structure of the parabasisphenoid determines the course of the internal carotid artery into the skull our findings allow us to discuss the early evolution of the carotid pattern and the turtle basicranium in new detail by surveying the main patterns of carotid circulation in extin

reconciliation of crosshole seismic velocities with well information in a layered sedimentary environment in sedimentary environments horizontal fine layering can cause significant complications when analyzing and comparing seismic data with different frequencies and propagation directions at the whitchester test site three boreholes penetrate upper carboniferous cyclical sediments involving interbedded carbonates sandstones and mudstones with seismic velocities ranging from less than 3 0 km s in the mudstones to over 4 5 km s in the carbonates initial crosshole results from two boreholes approximately 200 m deep and 75 m apart showed a poor correlation with the borehole logs recorded in a third intermediate borehole furthermore the tomographic images were inconsistent with the expected geology the objective of this paper is to reconcile the crosshole seismic data with the borehole log information the borehole information must be upscaled to match the resolution of the crosshole experiment however upscaling techniques based on backus averaging lead to the prediction of significant anisotropy of the order of 20 in places with a vertical symmetry axis this anisotropy is a result of a combination of fine layering and the intrinsic mineral anisotropy measured on the core samples although it is the layer induced anisotropy that dominates at the crosshole frequencies of 400 hz this prediction was tested by including anisotropy parameters into the analysis of the crosshole data using anisotropic velocity tomography in the central part of the final anisotropic velocity tomograms where the ray coverage is adequate these crosshole results are consistent with the anisotropy predictions once the anisotropy was properly accounted for the tomographic images are consistent with the layered nature of the geology at the site and they show the location and throw of a known fault in the section we conclude that at this site and at crosshole frequencies seismic layer induced anisotropy plays a significant role and must be accounted for when processing and interpreting crosshole seismic data

late quaternary vegetation and climate change in southeastern australia palynological evidence from marine core e55 6 abstract palynological analysis of core e55 6 obtained from off shore western victoria provides a record of vegetation and climate change in the southeastern south australian and western victorian region spanning much of the last 125 000 yr an accompanying oxygen isotope record provides a chronology for the sequence the pollen record suggests that maximum effective precipitation occurred during the height of the last interglacial oxygen isotope substage 5e with wet sclerophyll forest and rainforest widespread in the region effective precipitation appears to have decreased during substage 5d promoting the expansion of dry sclerophyll communities then increased slightly during substage 5c with the limited re occurrence of wetter forest types climatic conditions gradually became drier from substage 5b with the replacement of eucalypt dominated forest by more open heath and mallee type communities in the arid glacial conditions of isotopic stage 4 a brief phase of increased effective precipitation occurred during the interstadial stage 3 with limited expansion of eucalyptus followed by a steady decline in effective precipitation and the expansion of open heath and grass communities pollen is very sparse in the top section of the core making environmental interpretation difficult nevertheless it appears that grass and heath communities dominated the region during stage 2 there is no clear record of the holocene due to the presence of mudflow sediments in the top of the core the pollen evidence also suggests that continental shelf exposed as sea levels fell was colonised by a mosaic of coastal vegetation including myrtaceae dominated scrub eucalypt and casuarina woodland asteraceae and chenopodiaceae dominated heath and grassland the charcoal record expressed as a ratio to pollen concentration gives evidence of increased burning during the height of the last interglacial period most likely in response to increased fuel loads with the expansion of eucalypt dominated forest this record also indicates a second phase of increased burning commencing in stage 2 which gives possible evidence for increased anthropogenic activity in the region

what can the data on late survival of australian megafauna tell us about the cause of their extinction abstract roberts et al 2001a new ages for the last australian megafauna continent wide extinction about 46 000 years ago science 292 1888 1892 concluded that the extinction of australia s late pleistocene megafauna was an abrupt event that took place about 46 ka ago throughout the continent by placing the extinctions soon after the arrival of people in australia but before climate changes associated with the last glacial maximum this study implicated human impact as cause however the study was controversial because it excluded evidence mainly from archaeological sites containing disarticulated megafauna remains for survival of some megafauna well past 46 ka ago here i ask how our interpretation of the extinctions would be changed if this evidence were accepted contrary to climate change models of extinction the young megafauna sites are not concentrated in mesic refuges around the coast these sites do suggest that relatively small bodied megafauna species were the last to disappear as predicted by a version of the overkill hypothesis more work is needed to test the evidence for late survival of megafauna species in australia but at present this evidence supports overkill not climate change as the cause of the extinctions

disentangling the impacts of climate and human colonization on the flora and fauna of the australian arid zone over the past 100 ka using stable isotopes in avian eggshell abstract throughout the quaternary the flora and fauna of australia evolved and adapted to the high amplitude low and high frequency climate changes that characterized the ice age cycles however during the last glacial cycle between 120 and 15 ka unprecedented irreversible changes in flora and fauna occurred and in that same interval modern humans established their first firm presence in the landscape disentangling the impacts of the first order trend toward a colder drier planet through the late quaternary from the impacts of human colonization has been challenging from both the chronological and paleoenvironmental perspectives we utilize the stable isotopes of carbon and oxygen preserved in near continuous time series of dromaius emu eggshell from five regions across australia to provide independent reconstructions of ecosystem status and climate over the past 100 ka carbon isotopes are determined by the diet consumed by the female bird whereas oxygen isotopes record the status of local moisture balance in the months prior to breeding together 13 c and 18 o provide ecosystem status and climate from the same dated sample reducing correlation uncertainties between proxies combined with recent improvements in the chronologies of late quaternary shorelines fringing inland lake basins and deflation during arid times these data collectively reaffirm that australia generally became increasingly albeit irregularly drier from the last interglaciation through to the last glacial maximum dromaius eggshell 18 o documents peak aridity between 30 and 15 ka but shows no evidence of exceptional climate change between 60 and 40 ka in contrast dromaius 13 c diet documents an irreversible loss of the majority of palatable summer rainfall related c4 grasses across the australian arid zone between 50 and 45 ka about the same time that the giant megafaunal bird genyornis became extinct and coincident with human dispersal across the continent our data indicate that changes unique to australia occurred between 50 and 45 ka that led to a new climate vegetation relationship and an overall reduction in effective moisture across much of the continent the large summer rainfall dominated lakes of interior australia failed to re fill subsequently despite a wide range of global climate states a full explanation for the mechanisms behind these changes remains elusive but they are almost certainly related to human agency plausible explanations include a change in fire regime resulting from human lit fires a change in fire regime following extinction of megafaunal browsers and or a threshold response to increasing aridity of these the climate change explanation is least likely given the lack of evidence for unprecedented aridity between 60 and 40 ka and the successful adaptation of australian ecosystems to 2 5 ma of similar changes

el nino southern oscillation like variability during glacial terminations and interlatitudinal teleconnections interannual decadal variability in the equatorial pacific el nino southern oscillation enso induces climate changes at global scale but its potential influence during past global climate change is not yet well constrained new high resolution eastern equatorial pacific proxy records of thermocline conditions present new evidence of strong orbital control in enso like variability over the last 275 000 years recurrent intervals of saltier thermocline waters are associated with the dominance of la nina like conditions during glacial terminations coinciding with periods of low precession and high obliquity the parallel dominance of 13c depleted waters supports the advection of antarctic origin waters toward the tropical thermocline this oceanic tunneling is proposed to have reinforced orbitally induced changes in enso like variability composing a complex high and low latitude feedback during glacial terminations

southern ocean nitrogen and silicon dynamics during the last deglaciation abstract the reinvigoration of overturning in the southern ocean is hypothesized to have returned co2 from the deep ocean to the atmosphere at the end of the last ice age large peaks in opal accumulation have been put forward as evidence for an increase in wind driven upwelling between 10 and 15 ka here we use coupled nitrogen and silicon isotope records alongside opal accumulation rates to provide quasi quantitative estimates of southern ocean nutrient supply by upwelling and nutrient utilization across this interval significant changes in the consumption of n and si across the two opal accumulation peaks indicate major changes in both upwelling and nutrient demand we find n and si consumption to be relatively incomplete during peak opal accumulation at the onset of the deglaciation this indicates that nutrient supply was significantly enhanced the second deglacial peak in opal accumulation is associated with more complete si consumption and variable n consumption we suggest that this peak represents strong upwelling and more complete utilization of the available silicic acid pool differences between the si and n responses during opal peaks may stem from decreasing iron availability across the glacial termination the nutrient isotope evidence for excess nutrients during the deglaciation indicates that the high export productivity was insufficient to overcome the evasion of co2 to the atmosphere as a result of physical circulation changes previous work has demonstrated that the reinvigoration of overturning circulation during the deglaciation causes a transient peak in nutrient supply to the low latitudes this is supported by our data which indicate that relatively high macronutrient concentrations were maintained in the southern ocean surface waters that are incorporated into mode waters despite high demand

continuous 150 k y monsoon record from lake eyre australia insolation forcing implications and unexpected holocene failure our reconstructed history of lake eyre provides the first continuous continental proxy record of australian monsoon intensity over the past 150 k y this continental record s broad correspondence to the marine isotope record demonstrates that this very large catchment with its hydrology dependent on a planetary scale climate element responds to milankovitch scale climate forcing abrupt transitions from dry phases to wet phases ca 125 and 12 ka coincide with northern hemisphere winter insolation minima rather than southern hemisphere summer insolation maxima indicating that northern hemi sphere insolation exerts a dominant control over the intensity of the australian monsoon stratigraphic and dating uncertainties of other wet phases preclude conclusive correlation to specific insolation signals but within the uncertainties are consistent with northern hemisphere forcing regardless of the hemispheric forcing the low intensity of the early holocene australian monsoon by comparison with the last interglacial and particularly the last high level lacustrine event at 65 60 ka when all forcing elements were modest is an enigma that can be explained by a change in boundary conditions within australia

early human occupation at devil s lair southwestern australia 50 000 years ago abstract new dating confirms that people occupied the australian continent before the earliest time inferred from conventional radiocarbon analysis many of the new ages were obtained by accelerator mass spectrometry 14c dating after an acid base acid pretreatment with bulk combustion aba bc or after a newly developed acid base wet oxidation pretreatment with stepped combustion abox sc the samples charcoal came from the earliest occupation levels of the devil s lair site in southwestern western australia initial occupation of this site was previously dated 35 000 14c yr b p whereas the aba bc ages are indistinguishable from background beyond 42 000 14c yr b p the abox sc ages are in stratigraphic order to 55 000 14c yr b p the abox sc chronology suggests that people were in the area by 48 000 cal yr b p optically stimulated luminescence osl electron spin resonance esr ages u series dating of flowstones and 14c dating of emu eggshell carbonate are in agreement with the abox sc 14c chronology these results based on four independent techniques reinforce arguments for early colonization of the australian continent

homo floresiensis and the late pleistocene environments of eastern indonesia defining the nature of the relationship abstract evidence from liang bua a limestone cave on the island of flores in east indonesia provides a unique opportunity to explore the long term relationship between hominins and their environment occupation deposits at the site span 95 ka and contain abundant stone artefacts well preserved faunal remains and evidence for an endemic species of hominin homo floresiensis work at the site included detailed geomorphological and environmental analysis which has enabled comparisons to be drawn between changes in the occupational intensity in the cave using stone tool and faunal counts and changes in the environmental conditions using the characteristics of the sedimentary layers in the cave and speleothem records these comparisons demonstrate that h floresiensis endured rapidly fluctuating environmental conditions over the last 100 ka which influenced the geomorphological processes in the cave and their occupational conditions the intensity of occupation in the cave changed significantly between 95 and 17 ka with peaks in occupation occurring at 100 95 74 61 and 18 17 ka these correlate with episodes of channel formation and erosion in the cave which in turn correspond with high rainfall thick soils and high bio productivity outside in contrast periods of low occupational intensity correlate with reduced channel activity and pooling associated with drier periods from 94 to 75 and 36 to 19 ka this apparent link between intensity of hominin use of the cave and the general conditions outside relates to the expansion and contraction of the rainforest and the ability of h floresiensis to adapt to habitat changes this interpretation implies that these diminutive hominins were able to survive abrupt and prolonged environmental changes by changing their favoured occupation sites these data provide the basis for a model of human environment interactions on the island of flores with the addition of extra data from other sites on flores this model will provide a greater understanding of h floresiensis as a unique human species

new material of dracochelys eucryptodira sinemydidae from the junggar basin xinjiang people s republic of china a new specimen of dracochelys bicuspis documents the lower jaws and postcranial skeleton of this taxon a close relationship with hangaiemys is supported by the presence of nine neural bones with the sulcus between the fourth and fifth vertebral scute crossing the ninth neural the two taxa differ in the contacts of the first peripheral shape of the vertebral scutes and pattern of fenestration of the plastron dracochelys differs from sinemys wuerhoensis and s efremovi which also occur in the tugulu group in features of the carapace especially the arrangement of the posterior neurals and suprapygals

late quaternary milankovitch scale climatic change and variability and its impact on monsoonal australasia four pollen and charcoal records derived from marine cores around the northern perimeter of australia are examined to provide a regional picture of patterns causes and impacts of climate change over the last 100 300 ka the availability of radiocarbon dates and oxygen isotope records for the cores provides primary chronological control spectral analysis of components of these records demonstrates an overall importance of milankovitch frequencies with clear glacial interglacial cyclicity dominated by variation in precipitation in addition a number of pollen taxa as well as charcoal particles exhibit a 30 ka frequency that is considered from its relationship with biomass burning and with results of past modelling to reflect changes in the intensity of el nino southern oscillation enso variability pollen components of all records show a decline frequently stepwise in more fire sensitive vegetation and its replacement with more fire tolerant vegetation there is some evidence that this trend is linked to an onset or general increase in enso activity and perhaps also to variation in monsoon activity dating from about 300 ka bp that was caused by changes to oceanic circulation within the indonesian region the trend may have accelerated within the last 45 ka due to burning by indigenous people c 2003 elsevier b v all rights reserved

new material of sinemys testudines sinemydidae from the early cretaceous of china sinemys lens is redescribed on the basis of new material from the early cretaceous of shandong china and a new species of sinemys from the ordos basin in inner mongolia is recognized sinemys and manchurochelys are placed in the sinemydidae sensu stricto on the basis of the derived features of a small first suprapygal and an elongate narrow posterior lobe of the plastron sinemys is autapomorphic in the absence of a cervical scute the entry of the first vertebral onto the anterior margin of the carapace the absence of a pygal bone the entry of the fifth vertebral scute into the posterior margin of the carapace in that the riblike lateral projections of the last three costal bones fit between the adjacent peripherals and in the isolation of the epiplastra from the hyoplastra by lateral expansion of the entoplastron sinemys gamera sp nov from the early cretaceous luohandong formation of the ordos basin inner mongolia is characterized by the presence of a flat carapace with an abbreviated poste

late quaternary fluctuations of palaeoproductivity in the murray canyons area south australian continental margin abstract two sediment cores from the murray canyons area south of kangaroo island south australia were investigated for proxy records to reconstruct past productivity of the surface waters in the area over the last 175 ka the proxies used included concentrations of aragonite low and high mg calcite total carbonate total organic carbon sulfur and 13c of globigerina bulloides cyclic increases in palaeoproductivity were observed to be in tune with insolation minima at 30 s the atmospheric conditions during insolation minima were comparable to present winter patterns when strong westerly winds dominate over the area and bring dust from the central desert areas during the last insolation minimum last glacial maximum lgm the murray canyons laid directly under the eastern australian dust plume dust could have fertilized surface waters and initiated the observed productivity increases on a precessional time scale the core from the more westerly canyons is richer in organic matter this could be attributed to the influx of organic matter from shallower water which is carried by an overflow of hypersaline water from the spencer gulf to the deep ocean using the western canyons as conduits there is no evidence that the palaeo murray river which debouches close to the core sites during sealevel lowstands was a major source of nutrients for surface waters although total carbonate concentrations remained high planktonic foraminifers were fewer in numbers during these periods possibly due to reduced light penetration caused by suspended river material a deglacial minimum in 13c of globigerina bulloides observed in other cores from the southern hemisphere and attributed to a major hydrographic change south of the polar front is also visible in our two cores thus attesting to the global significance of the event

anisotropic 3d full waveform inversion abstractwe have developed and implemented a robust and practical scheme for anisotropic 3d acoustic full waveform inversion fwi we demonstrate this scheme on a field data set applying it to a 4c ocean bottom survey over the tommeliten alpha field in the north sea this shallow water data set provides good azimuthal coverage to offsets of 7 km with reduced coverage to a maximum offset of about 11 km the reservoir lies at the crest of a high velocity antiformal chalk section overlain by about 3000 m of clastics within which a low velocity gas cloud produces a seismic obscured area we inverted only the hydrophone data and we retained free surface multiples and ghosts within the field data we invert in six narrow frequency bands in the range 3 to 6 5 hz at each iteration we selected only a subset of sources using a different subset at each iteration this strategy is more efficient than inverting all the data every iteration our starting velocity model was obtained using standard psdm model bui

kalasinemys a new xinjiangchelyid turtle from the late jurassic of ne thailandh tong et al new xinjiangchelyid turtle from ne thailand a new xinjiangchelyid turtle kalasinemys prasarttongosothi n gen n sp is described on the basis of skull and shell material from the upper jurassic phu kradung formation at phu noi locality kalasin province in ne thailand this second xinjiangchelyid turtle from phu noi is distinct from phunoichelys thirakhupti by the smooth shell surface the presence of a cervical notch and vertebral 1 narrower than nuchal the skull presents an arterial system characteristic of the xinjiangchelyidae basal eucryptodira and its outline is similar to that of annemys spp known from the middle late jurassic of china and mongolia but distinct from the latter mainly by the wider triturating surface smaller foramen palatinum posterius and the shape of the prefrontal and frontal as well as that of the basisphenoid and basioccipital based on the turtle assemblages the correlation with mainland asia further supports a late jurassic age for the lower part of the phu kradung formation where phu noi site is located stratigraphically our study provides new insight on the evolution of the basal eucryptodiran turtles in asia

inverse theory applied to multi source cross hole tomography part 1 acoustic wave equation method1 frequency domain methods are well suited to the imaging of wide aperture cross hole data however although the combination of the frequency domain with the wavenumber domain has facilitated the development of rapid algorithms such as diffraction tomography this has also required linearization with respect to homogeneous reference media this restriction and association restrictions on source receiver geometries are overcome by applying inverse techniques that operate in the frequency space domain in order to incorporate the rigorous modelling technique of finite differences into the inverse procedure a nonlinear approach is used to reduce computational costs the method of finite differences is applied directly to the frequency domain wave equation the use of high speed high capacity vector computers allow the resultant finite difference equations to be factored in place in this way wavefields can be computed for additional source positions at minimal extra cost allowing inversions to be generated using data from a very large number of source positions synthetic studies show that where weak scatter approximations are valid diffraction tomography performs slightly better than a single iteration of non linear inversion however if the background velocities increase systematically with depth diffraction tomography is ineffective whereas non linear inversion yields useful images from one frequency component of the data after a single iteration further synthetic studies indicate the efficacy of the method in the time lapse monitoring of injection fluids in tertiary hydrocarbon recovery projects

silicic acid leakage from the southern ocean opposing effects of nutrient uptake and oceanic circulation 1 studies invoking the silicic acid leakage hypothesis to explain events of high biogenic opal deposition at low latitudes did not consider variations in formation rate of southern ocean intermediate waters comparison of 30si records from the southern ocean to records of biogenic opal accumulation from low latitude upwelling systems indicates a strong negative correlation between the silicic acid content of southern ocean surface waters and opal deposition at low latitudes during the last 80 kyr bp this implies that si leakage was somehow rendered ineffective when the silicic acid content of southern ocean waters was high comparison of opal accumulation records with records of intermediate water formation rates suggests that lower rates of intermediate water formation offset the higher silicic acid content of these water masses during glacial periods this indicates that physical processes that control intermediate water transport dominate over biological processes that set the silicic acid content of antarctic surface waters in determining the magnitude of silicic acid leakage from the southern ocean

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

seismic waveform inversion in the frequency domain part 2 fault delineation in sediments using crosshole data a crosshole experiment was carried out in a layered sedimentary environment in which a normal fault is known to cut through the section initial traveltime inversions produced stable but low resolution images from which the fault could be only vaguely inferred to image the fault wavefield inversion was used to produce a velocity model consistent with the detailed phase and amplitude of the data at a number of frequencies our wavefield inversion scheme uses a classical descent type algorithm for decreasing the data misfit by iteratively computing the gradient of this misfit by repeated forward and backward propagations our propagator is a full wave equation frequency domain acoustic finite difference method the use of the frequency space domain yields computational advantages for multisource data and allows an easy incorporation of viscous effects by running wavefield inversion on the field data a quantitative velocity image was produced that yielded a significantly improved image of the fault when compared with the original traveltime inversions because the original field data were noisy and contained a high degree of multiple scattering from the layering of the sediments the transmitted arrivals were selectively windowed to enhance the image the sediments at the site were strongly attenuating we therefore used a viscoacoustic model during the modeling and the inversion that correctly simulated the observed decrease in amplitude with increasing frequency and source receiver offset furthermore since the traveltime inversion indicated a high degree of anisotropy at the site a fixed homogeneous level of anisotropy was used during the inversion tests at varying levels of anisotropy confirmed the improvement in image quality and in data fit when anisotropy was incorporated the final image was verified by examining the distribution of the residuals in the frequency domain by comparing time domain modeled wavefields with the observed data and by direct comparison with borehole logs

abrupt vegetation change after the late quaternary megafaunal extinction in southeastern australia the extinction of megafauna in australia about 43 000 years ago has been linked to both human arrival and vegetation change marine sediment analyses from the east coast of australia suggest that vegetation change was a result rather than cause of the extinction

palaeontology extinction promoted fire the extinction of megafauna in australia roughly coincided with shifts in vegetation and fire regimes sediment geochemistry shows that the vegetation shift followed the extinction indicating that the loss of browsers promoted fire and altered plant composition

would the australian megafauna have become extinct if humans had never colonised the continent comments on a review of the evidence for a human role in the extinction of australian megafauna and an alternative explanation by s wroe and j field a critical comment on a review of the evidence for a human role in the extinction of australian megafauna and an alternative explanation by s wroe and j field is presented the authors have highlighted a range of ideas under consideration and provided a selective interpretation which does not come to terms with biology and ignores or misinterprets current evidence they rely heavily on the ages reported by roberts et al 2001 to argue for a gradual attenuation of the megafauna they propose a staggered series of extinctions throughout the middle and late pleistocene with many taxa lost during the penultimate glacial maximum pgm 140 130 ka and relatively few species persisting they ignore measurement uncertainties associated with the ages which when properly considered means that 20 rather than eight of the species they list have last appearance ages consistent with 45 ka

nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media crosshole seismic tomography often is applied to image the velocity structure of an interwell medium if the rocks are anisotropic the tomographic technique must be adapted to the complex situation otherwise it leads to a false interpretation we propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes this method is based on a new version of the first order traveltime perturbation equation it directly uses the derivative of the phase velocity rather than the eigenvectors of the body wave modes to overcome the singularity problem for application to the two quasi shear waves we applied an iterative nonlinear solver incorporating our kinematic ray tracing scheme and directly compute the jacobian matrix in an arbitrary reference medium this reconstructs the five elastic moduli or thomsen parameters from the first arrival traveltimes of the three seismic body waves qp qsv qsh in strongly and weakly anisotropic media we conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock reconstructing a fault embedded in a strongly anisotropic background and imaging a complicated four layer model containing a small channel and a buried dipping interface we compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme which showed the capability and superiority of the new scheme for crosshole tomographic imaging

esr and u series analyses of faunal material from cuddie springs nsw australia implications for the timing of the extinction of the australian megafauna abstract the timing and cause of late pleistocene faunal extinctions in australia are subjects of a debate that has become polarised by two vigorously defended views one contends that the late pleistocene extinction was a short event caused by humans colonising the australian continent whereas the other promotes a gradual demise of the fauna over a period of at least 10 20 ka due to a combination of climatic changes and ecological pressures by humans cuddie springs is central to this debate as it is the only site known in continental australia where archaeological and megafauna remains co occur we have analysed more than 60 bones and teeth from the site by laser ablation icp ms to determine u and th concentrations and distributions and those with sufficiently high u concentrations were analysed for u series isotopes twenty nine teeth were analysed by esr these new results as well as previously published geochronological data contradict the hypothesis that the clastic sediments of stratigraphic unit 6 su6 are in primary context with the faunal archaeological and other materials found in su6 and that all have ages consistent with the optically stimulated luminescence osl estimates of 30 36 ka these young osl results were used to argue for a relatively recent age of the extinct fauna our results imply that su6 is either significantly older than the osl results or that a large fraction of the faunal material and the charcoal found in su6 was derived from older lateral deposits our u and th laser ablation icpms results as well as the ree profiles reported by trueman et al 2008 comparing rates of recystallisation and the potential for preservation of biomolecules from the distribution of trace elements in fossil bones c r palevol general paleontology taphonomy and fossilization 7 145 158 contradict the interpretation of previously reported rare earth element compositions of bones and the argument based thereon for the primary context of faunal material and clastic sediments in su6 layers

cryptic meteoric diagenesis in freshwater bivalves implications for radiocarbon dating shells of freshwater bivalves are commonly used for radiocarbon dating late pleistocene archaeological and vertebrate fossil sites thus providing important constraints on late pleistocene human dispersal and megafauna extinction hypotheses the reliability of bivalve shells for dating rests partly on the ease with which subsequent diagenetic alteration can be recognized typically wherein original shell aragonite is replaced by calcite in meteoric environments here we document late pleistocene freshwater bivalve shells wherein meteoric diagenesis involved syntaxial overgrowth of aragonite cement on original aragonite shell biocrystals aragonite cement was identified in situ using raman microspectroscopy and formed rather than calcite as a result of unusually high mg ca ratios in local groundwaters thus altered shells contain diagenetic 14c rendering their dates unreliable but they may slip past common vetting techniques because 1 epitaxial cements are not readily apparent petrographically because they are in optical continuity with adjacent biocrystals 2 x ray diffraction indicates that no calcite is present 3 alteration is not apparent in cathodoluminescence studies and 4 stable isotopes of c and o are difficult to interpret in shells that originate in terrestrial meteoric environments hence although freshwater with a high mg ca ratio is not common groundwater chemistry should be considered before accepting bivalve based radiocarbon dates uncritically more broadly meteoric diagenesis in carbonate rocks is generally characterized by the dissolution of aragonite or its conversion to calcite our data show that such is not invariably the case even in fully terrestrial freshwater systems

man and megafauna in tasmania closing the gap abstract recent discussion on the late pleistocene extinction of the australian megafauna has revolved around interpretation of several key fossil sites in tasmania it has been suggested that humans did not arrive in tasmania until after the megafauna became extinct or did not hunt now extinct megafauna and therefore that humans cannot be implicated in the extinctions radiocarbon results from these sites indicate that the youngest extinct megafauna are close to charcoal ages from the oldest archaeological deposits although difficulties have arisen in establishing chronologies because most relevant sites have ages near the limit for radiocarbon analysis we report a series of new radiocarbon ages 13 c 15 n and c n ratios on collagen and dentine fractions from skeletal remains in the mount cripps karst area and the mowbray swamp both in northwestern tasmania and discuss the reliability of ages from these and other sites we also report the discovery of an articulated simosthenurus occidentalis skeleton at mt cripps that represents only the second directly dated extinct megafaunal taxon with a reliable age our results suggest that c n ratios measured on collagen or dentine are not an infallible guide to radiocarbon age reliability we confirm previous reports of a temporal overlap between the megafaunal and archaeological records in tasmania but the presence of archaeological evidence and megafauna with the same age at the same site has not yet been demonstrated at least two megafaunal taxa the now extinct protemnodon anak and a giant pleistocene form of the extant macropus giganteus were still present in tasmania after 43 ka when human crossing of the bassian landbridge from mainland australia first became sustainable

updating martin s global extinction model australia has been cited as a weak link in anthropogenic models of megafauna extinction but recent work suggests instead that the evidence for rapid extinction shortly after human arrival is robust the global model is revisited based on the contention that late pleistocene megafauna extinctions took place rapidly on islands and some islands such as australia and the americas are much larger than others modern dating methods are increasingly able to refine chronologies and careful scrutiny suggests that hundreds of dates should be deleted from archives an updated summary of results from new zealand north america and australia is presented with a brief discussion on why temperate refugia offering protection from climate change ultimately did not work strongly supporting the global extinction hypothesis pioneered by paul martin

crosshole seismic waveform tomography ii resolution analysis summary in an accompanying paper we used waveform tomography to obtain a velocity model between two boreholes from a real crosshole seismic experiment as for all inversions of geophysical data it is important to make an assessment of the final model to determine which parts of the model are well resolved and can confidently be used for geological interpretation in this paper we use checkerboard tests to provide a quantitative estimate of the performance of the inversion and the reliability of the final velocity model we use the output from the checkerboard tests to determine resolvability across the velocity model such tests can act as good guides for designing appropriate inversion strategies here we discovered that by including both reference model and smoothing constraints in initial inversions and then relaxing the smoothing constraint for later inversions an optimum velocity image was obtained additionally we noticed that the performance of the inversion was dependent on a relationship between velocity perturbation and checkerboard grid size larger velocity perturbations were betterresolved when the grid size was also increased our results suggest that model assessment is an essential step prior to interpreting features in waveform tomographic images

crosshole seismic waveform tomography i strategy for real data application summary the frequency domain version of waveform tomography enables the use of distinct frequency components to adequately reconstruct the subsurface velocity field and thereby dramatically reduces the input data quantity required for the inversion process it makes waveform tomography a computationally tractable problem for production uses but its applicability to real seismic data particularly in the petroleum exploration and development scale needs to be examined as real data are often band limited with missing low frequencies a good starting model is necessary for waveform tomography to fill in the gap of low frequencies before the inversion of available frequencies in the inversion stage a group of frequencies should be used simultaneously at each iteration to suppress the effect of data noise in the frequency domain meanwhile a smoothness constraint on the model must be used in the inversion to cope the effect of data noise the effect of non linearity of the problem and the effect of strong sensitivities of short wavelength model variations in this paper we use frequency domain waveform tomography to provide quantitative velocity images of a crosshole target between boreholes 300 m apart due to the complexity of the local geology the velocity variations were extreme between 3000 and 5500 m s 1 making the inversion problem highly non linear nevertheless the waveform tomography results correlate well with borehole logs and provide realistic geological information that can be tracked between the boreholes with confidence

reflection seismic waveform tomography 1 in seismic waveform tomography if using reflection data with limited source receiver offsets it is difficult to reconstruct the deep part of the subsurface velocity model we present two approaches to tackle this problem layer stripping and weighted updating in a layer stripping procedure we replace the top portion of seismic data with synthetics generated from the previous layer inversion and make the current inversion focus on the minimization of the data misfit corresponding to the deep part of the model to improve efficiency we use only sparsely sampled frequency data in the deeper layer inversions unlike the first layer inversion where we use densely sampled frequency data as usual the sparsely sampled frequencies together have the full wave number coverage for effective imaging combined use of dense and sparse sampling in frequency is a compromise between resolution and efficiency as it reduces the number of iterations needed in layer stripping inversion while still producing a good image in the second scheme we apply depth dependent weights to model updates in order to improve the convergence in an iterative solution the weighting is inversely proportional to the ray density variation along the depth and is mathematically equivalent to the application of an inverse hessian matrix which sharpens the gradient vector for model updating for real seismic data we transfer point source shot records to line source records by partial amplitude compensation and phase adjusting before inputting it to the waveform tomography we perform traveltime inversion to generate a reliable layered velocity model and then waveform tomography to produce a high resolution image of the subsurface model through frequency domain iteration

the timing and cause of megafauna mass deaths at lancefield swamp south eastern australia abstract lancefield swamp south eastern australia was one of the earliest sites to provoke interest in pleistocene faunal extinctions in sahul pleistocene australia new guinea the systematic investigation of the deposit in the early 1970s identified megafaunal remains dominated by the 100 200 kg kangaroo macropus giganteus titan associated radiocarbon ages indicated that the species was extant until c 30 000 bp suggesting significant overlap with human settlement of sahul this evidence was inconsistent with contemporary models of rapid human driven extinctions instead researchers inferred ecological tethering of fauna at lancefield swamp due to intense drought precipitated localised mass deaths consistent with late pleistocene climatic variability later investigations in another part of the swamp the mayne site remote to the initial investigations concluded that mass flow disturbed this area and electron spin resonance esr analyses on megafauna teeth returned wide ranging ages to clarify site formation processes and dating of lancefield swamp we excavated new test pits next to previous trenches in the classic and mayne sites we compared absolute chronologies for sediments and teeth sedimentology palaeo topography taphonomy and macropod age at death across the swamp luminescence dating of sediments and esr analysis of teeth returned ages between c 80 000 and 45 000 years ago we found no archaeological remains in the bone beds and evidence of carnivore activity and fluvial action in the form of reactivated spring flow the latter disturbed limited parts of the site and substantial areas of the bone beds remained intact the faunal assemblage is dominated by megafaunal adult macropus consistent with mass die offs due to severe drought such droughts appear to have recurred over millennia during the climatic variability of marine isotope stages 4 and 3 these events began tens of millennia before the first appearance of aboriginal people in sahul and only the very youngest fossil deposits could be coeval with the earliest human arrivals therefore anthropogenic causes cannot be implicated in most if not all of mass deaths at the site climatic and environmental changes were the main factors in site formation and megafauna deaths at lancefield swamp

mammalian responses to pleistocene climate change in southeastern australia resolving faunal responses to pleistocene climate change is vital for differentiating human impacts from other drivers of ecological change while 90 of australia s large mammals were extinct by ca 45 ka their responses to glacial interglacial cycling have remained unknown due to a lack of rigorous biostratigraphic studies and the rarity of terrestrial climatic records that can be related directly to faunal records we present an analysis of faunal data from the naracoorte caves in southeastern australia which are unique not only because of the species richness and time depth of the assemblages that they contain but also because this faunal record is directly comparable with a 500 k y speleothem based record of local effective moisture our data reveal that despite significant population fluctuations driven by glacial interglacial cycling the species composition of the mammal fauna was essentially stable for 500 k y before the late pleistocene extinctions larger species declined during a drier interval between 270 and 220 ka likely reflecting range contractions away from naracoorte but they then recovered locally persisting well into the late pleistocene because the speleothem record and prior faunal response imply that local conditions should have been favorable for megafauna until at least 30 ka climate change is unlikely to have been the principal cause of the extinctions