seismic reflection borehole and outcrop geometry of late wisconsin tills at a proposed landfill near toronto ontario the search for new landfill sites in the greater toronto area of southern ontario canada is producing a wealth of data regarding the subsurface stratigraphy and geometry of late wisconsin 25 ka

early human occupation of a maritime desert barrow island north west australia abstract archaeological deposits from boodie cave on barrow island northwest australia reveal some of the oldest evidence for aboriginal occupation of australia as well as illustrating the early use of marine resources by modern peoples outside of africa barrow island is a large 202 km 2 limestone continental island located on the north west shelf of australia optimally located to sample past use of both the pleistocene coastline and extensive arid coastal plains an interdisciplinary team forming the barrow island archaeology project biap has addressed questions focusing on the antiquity of occupation of coastal deserts by hunter gatherers the use and distribution of marine resources from the coast to the interior and the productivity of the marine zone with changing sea levels boodie cave is the largest of 20 stratified deposits identified on barrow island with 20 m 3 of cultural deposits excavated between 2013 and 2015 in this first major synthesis we focus on the dating and sedimentology of boodie cave to establish the framework for ongoing analysis of cultural materials we present new data on these cultural assemblages including charcoal faunal remains and lithics integrated with micromorphology sedimentary history and dating by four independent laboratories first occupation occurs between 51 1 and 46 2 ka overlapping with the earliest dates for occupation of australia marine resources are incorporated into dietary assemblages by 42 5 ka and continue to be transported to the cave through all periods of occupation despite fluctuating sea levels and dramatic extensions of the coastal plain the changing quantities of marine fauna through time reflect the varying distance of the cave from the contemporaneous shoreline the dietary breadth of both arid zone terrestrial fauna and marine species increases after the last glacial maximum and significantly so by the mid holocene the cave is abandoned by 6 8 ka when the island becomes increasingly distant from the mainland coast

chronology of early eocene marine and terrestrial strata baja california mexico we present a multidisciplinary study of the marine and terrestrial biostratigraphy and paleomagnetism of early eocene intertonguing marine and continental strata from the punta prieta area central baja california mexico the mammalian fauna is assigned to the wasatchian north american land mammal age rather than the clarkforkian assignment of earlier studies extensive molluscan assemblages from intertonguing marine strata are correlated to the restricted capay stage and therefore are middle ypresian middle early eocene in age this correlation is supported by a benthic foraminiferal assemblage assigned to the penutian ulatisian stage and the ostracode buntonia early eocene first appearance this study is only the second that provides direct correlation of early paleogene marine and terrestrial biochronologies in north america our correlation indicates that part of the wasatchian mammal age is correlative with the ypresian age as had been suggested previously from indirect evidence all of the paleomagnetic sites from three sections are reversely magnetized the associated middle early eocene biochronologic information permits correlation of this reversed polarity interval to chron c23r or the reversed polarity interval within chron c24n wasatchian mammal assemblages now are known from northern canada ellesmere island to central baja all available geochronologic information indicates that these assemblages are synchronous across broad intracontinental areas our early eocene paleomagnetic study provides the first early cenozoic results from the baja peninsula and the first direct constraint on the early cenozoic plate tectonic motion of the peninsula our results indicate that baja california was in its pre gulf of california position sutured adjacent to the northern mexican mainland prior to the middle early eocene these results conflict with some previous interpretations of the motion of baja discrepancies may be caused by failure to treat small terranes as discrete potentially independent mobile land masses

revised age of the late neogene terror bird titanis in north america during the great american interchange the giant flightless terror bird titanis walleri is known from florida and texas during the late neogene the age of t walleri is problematic because this taxon co occurs with temporally mixed i e time averaged faunas at two key sites thus prior to this study t walleri from the santa fe river florida type locality was either as old as late pliocene ca 2 2 ma or as young as latest pleistocene ca 15 ka likewise t walleri from the nueces river texas was either early pliocene ca 5 ma or latest pleistocene ca 15 ka in order to better resolve this age range the rare earth element ree patterns of t walleri from the santa fe river florida were compared to two biochronologically distinctive groups late pliocene versus late pleistocene of fossil mammals from the same locality similarly the ree patterns of t walleri from texas were compared to two groups early pliocene versus latest pleistocene of fossil mammals from the same locality the ree patterns of t walleri from florida are indistinguishable from those of the co occurring late pliocene mammals likewise the ree pattern of t walleri from texas is indistinguishable from those of the co occurring early pliocene mammals given these ree constraints the revised age of t walleri is early pliocene in texas ca 5 ma and late pliocene ca 2 2 1 8 ma in florida as such t walleri is interpreted as an early immigrant during the great american interchange prior to the formation of the isthmian land bridge no evidence currently exists for pleistocene t walleri in north america

late quaternary mega lakes fed by the northern and southern river systems of central australia varying moisture sources and increased continental aridity optically stimulated and thermoluminescence ages from relict shorelines along with accelerator mass spectrometer 14c ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to lake mega frome in southern central australia during the late quaternary additional lacustrine palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka confirming that lakes mega frome and mega eyre were joined to create the largest system of palaeolakes on the australian continent as recently as 50 47 ka the palaeohydrological record indicates a progressive shift to more arid conditions with marked drying after 45 ka subsequently lake mega frome has filled independently at 33 31 ka and at the termination of the last glacial maximum to volumes some 40 times those of today further sequentially declining filling episodes to volumes 25 10 those of today occurred immediately prior to the younger dryas stadial in the mid holocene and during the medieval climatic anomaly southern hemisphere summer insolation maxima are a poor predictor of palaeolake filling episodes an examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced southern ocean circulation and strengthened tropical moisture sources

a stalagmite record of holocene indonesian australian summer monsoon variability from the australian tropics oxygen isotopic data from a suite of calcite and aragonite stalagmites from cave kni 51 located in the eastern kimberley region of tropical western australia represent the first absolute dated high resolution speleothem record of the holocene indonesianeaustralian summer monsoon iasm from the australian tropics stalagmite oxygen isotopic values track monsoon intensity via amount effects in precipitation and reveal a dynamic holocene iasm which strengthened in the early holocene decreased in strength by 4 ka with a further decrease from w2 to 1 ka before strengthening again at 1 ka to years to levels similar to those between 4 and 2 ka the relationships between the kni 51 iasm reconstruction and those from published speleothem time series from flores and borneo in combination with other data sets appear largely inconsistent with changes in the position and or organization of the intertropical convergence zone itcz instead we argue that the el nino southern oscillation enso may have played a dominant role in driving iasm variability since at least the middle holocene given the muted modern monsoon rainfall responses to most el nino events in the kimberley an impact of enso on regional monsoon precipitation over northwestern australia would suggest non stationarity in the long term relationship between enso forcing and iasm rainfall possibly due to changes in the mean state of the tropical pacific over the holocene

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

road impacted sediment and water in a lake ontario watershed and lagoon city of pickering ontario canada an example of urban basin analysis abstract the world is increasingly urban but there are few studies of how contaminated water and sediment move through urban basins with their built landscapes and complexly disturbed geology the central canadian city of pickering ontario sprawls across a small 27 km 2 densely urbanized pop 53 000 watershed and is underlain by pleistocene glacial sediments and thick artificial fill deposits almost 80 of the area is hardened by impervious cover road and rail lines cover 40 and include canada s busiest highway 12 lane highway 401 177 000 vehicles per day in 2003 the basin discharges to lake ontario through a small 85 ha shallow 2000 mg l 1 occur during winter thaws in creeks downstream of the highway enhanced stream bank erosion as a consequence of flashy storm runoff from road surfaces moves 100 tonnes of contaminated sediment to frenchman s bay each year instantaneous suspended sediment concentrations in storm runoff are as high as 1600 g m 3 and loadings of sulphate so 4 2 nutrients reach 594 kg h 1 metals and e coli in road runoff are all elevated well above canadian water quality standards these findings underscore findings from other urban areas regardless of regional climate that transportation corridors are a major global source of contaminated water and sediment

hydrogeology of the coventry region uk an urbanized multilayer dual porosity aquifer system abstract the coventry groundwater investigation has researched the sources and movement of chlorinated hydrocarbon solvents in the groundwater system underlying the coventry region the hydrogeological scene is set in this paper as a basis for the other aspects of the investigation which are reported in the other papers in this volume the deep intercalcated sandstones and mudstones of the permo carboniferous which underly the study area behave as a multilayer aquifer although individual aquifer units are not regionally extensive the sandstone units are fractured and behave as dual porosity aquifers with rapid tracer movement in fractures and diffusion into the low permeability but porous matrix the water balance of the groundwater system has changed from natural conditions because of man s influence although direct recharge has been reduced by the impermeable surfaces of roads and towns substantial extra recharge arises in the urban areas from leaking water mains

magnetic polarity stratigraphy of inchasi a pliocene mammal bearing locality from the bolivian andes deposited just before the great american interchange abstract the newly discovered section at inchasi located about 50 km southeast of potosi bolivia in the eastern cordillera consists of about 120 m of undeformed terrestrial sediments containing fossil mammals paleomagnetic analysis of 54 sites indicates a polarity pattern with an estimated duration of about 0 64 ma the rich inchasi local fauna indicates a montehermosan and or chapadmalalan land mammal age pliocene given these constraints inchasi correlates from the interval between the late gilbert within the cochiti subchron to the early gauss within the mammoth subchron chrons that is between about 4 0 and 3 3 ma the distinct lack of north american mammals in the inchasi local fauna provides some of the first well calibrated evidence that the great american interchange occurred after about 3 0 ma as has been previously stated based on other calibrations of the earliest immigrant uquian faunas

exploring sea country through high resolution 3d seismic imaging of australia s nw shelf resolving early coastal landscapes and preservation of underwater cultural heritage abstract almost 2 million square km of australia s continental shelf was flooded following the termination of the last glacial maximum and with it the cultural heritage of the first arrival and coastal occupation of australia beginning some 65 000 years ago in order to prospect for this missing cultural record we must first identify submerged coastal landscapes and landforms that likely provided favourable environments for occupation and resource use however this task is challenged by the sheer size of the australian continental margin to help address this we use industry 3d seismic datasets that cover vast areas of australia s continental shelf to map seafloor bathymetry at high resolution 10 25 m our study focuses an area of 6500 square km on the mid outer shelf regions proximal to barrow island the 3d seismic bathymetry revealed a highly complex and geomorphically mature coastal landscape preserved at depths of 70 75 m below sea level including coastal barrier dunes lagoonal systems tidal flats and estuarine channels based on the depth of the submerged shorelines and reconstructed sea level curves the age range of these coastal landforms is constrained to marine isotope stage 3 57 29 ka which overlaps with the known onset of occupation at barrow island and the wider carnarvon bioregion and the adjacent pilbara such feature preservation has significant geoheritage value but also allows for human behavioural ecology modelling and provides targets for future dating and site survey

volcanism in aboriginal australian oral traditions ethnographic evidence from the newer volcanics province abstract this article collects and presents nineteenth century ethnographic evidence from the newer volcanics province of australia and explores how volcanism was recorded and understood in aboriginal oral traditions it investigates whether aboriginal australian oral traditions can be understood as persistent eyewitness accounts of volcanic eruptions in the newer volcanics province how and what kind of geological and volcanological knowledge was embedded within aboriginal australian oral traditions and considers what value the ethnographic evidence has for understanding both the socio cultural and geological histories of the newer volcanics province

radiocarbon evidence for mid late holocene changes in southwest pacific ocean circulation variability in the southwest sw pacific ocean circulation is influenced by the changes in the south pacific subtropical gyre and its western boundary current the east australian current eac the eac plays a significant role in transporting warm well ventilated nutrient poor waters to more temperate higher latitudes recent climate changes associated with eac intensification have led to anomalous warming in the south tasman with implications for marine ecosystems and environment a clear understanding of the significance of these changes requires knowledge of past natural variability here we have reconstructed a 4500 year record of regional sea surface radiocarbon reservoir ages r and local reservoir effects r our results reveal the centennial scale variability over the last 4500 years with r ranges as large as 390 14c yr older r 410 14c yr between 1610 to 1860 a d in our record corresponding to the little ice age suggests a weaker influence of the eac in the south tasman between 4000 and 1900 cal years b p r and r were significantly younger than the modern with values of 170 and 130 14c yr respectively indicating increased eac transport of tropical waters into the south tasman we propose that the large r variability was influenced by strong and abrupt el nino events which punctuated the muted el nino southern oscillation enso period in the mid late holocene and enabled increased westward flow of gyre waters into the sw pacific the strengthening of the eac extension appears to have been a response to the precession modulated enso southern annular mode interactions

land mammal ages faunal heterochrony and temporal resolution in cenozoic terrestrial sequences traditionally land mammal biochronology has subdivided the cenozoic into discernible time intervals with an average duration of about 3 5 times 10 6 years recent applications of chronological tools particularly magnetic polarity stratigraphy have increased the power of resolution by an order of magnitude so that time intervals of about 3 times 10 5 years can be discerned in terrestrial sequences this increased power of resolution has significant paleontological ramifications examples are cited of heterochronous time transgres sive datum planes however recently proposed examples of heterochrony of entire early cenozoic land mammal faunas result from incorrect correlations to the time scale given the recently increased power of temporal resolution it is possible to assess critically the quality of chronological data that have been used to propose or support drastic paleontological hypotheses such as faunal heterochrony heterochrony of entire land mammal faunas has not yet been documented

fission track dating of volcanically derived sedimentary rocks depositional ages of sedimentary rocks can be determined using fission track single grain ages on zircons from layers of volcanic ash or bentonite even when the layers have been contaminated by older grains this is done by compiling an age probability distribution or age spectrum for a sample from individual grain ages an age spectrum is a simple and unambiguous way of testing for contamination and extracting useful age information the youngest peak in the age spectrum approximates the time of deposition in most contaminated samples 30 or more grains should be counted to produce a reliable spectrum however useful reproducible ages can be obtained by counting less than 10 grains in samples where most of the older contaminating grains can be removed the few older grains that remain after removing the obviously abraded ones may then be eliminated by examining the age spectrum although ages determined in this way are probably not precise enough for use in defining stratigraphic boundaries they still provide a means of obtaining an isotopic age in sediments that cannot be dated by other radiometric methods 18 references 3 figures 3 tables

the potential for discovery of new submerged archaeological sites near the dampier archipelago western australia abstract the islands of the dampier archipelago preserve a probable 30 000 year archaeological record that reflects the change from a continental to an island environment following post glacial sea level rise the geomorphological history of the dampier archipelago region in combination with preliminary hydrodynamic modelling of past tidal regimes provides the basis for a new model of how the shelf landscape may have developed between the last glacial maximum c 20 ka bp through the holocene marine transgression and up to the present day using first order geomorphological principles an assessment is made of the key late pleistocene and holocene sediment bodies that may preserve archaeological deposits we show that archaeology is most likely to be present in deposits associated with the early phases of inundation of the dampier archipelago dating from around 9 7 ka bp at this time relative sea levels were around 30 m to 15 m which was when coastal configuration was complex and the variety and scale of intertidal and shallow sub tidal environments wide in contrast we anticipate that coastal archaeology older than 12 ka bp when the post glacial sea levels were below 50 m will have been exposed to a phase of faster tidal currents on the continental shelf and hence eroded or poorly preserved our study aims to improve prospection for and later management of the as yet unknown submerged elements of west australia s rich archaeological heritage

geochronology of hemphillian blancan aged strata guanajuato mexico and implications for timing of the great american biotic interchange abstract we present new geochronologic magnetostratigraphy fission track and 40ar 39ar radioisotopic dates biostratigraphy data constraining the age of three separate sequences and a composite section from guanajuato mexico those data make this one of the most complete and precisely age calibrated sequences in north america spanning the hemphillian blancan north american land mammal age nalma boundary interval and the data further constrain the timing and pattern of the great american biotic interchange gabi in total 196 samples 77 sites were used to construct the magnetic polarity stratigraphies with eight fission track analyses and four new 40ar 39ar radioisotopic dates the sections sampled are possibly latest miocene to late pliocene in age spanning about 2 7 m yr 5 5 2 7 ma from chrons c3n 4n or c3r to c2an 1n the radioisotopic dates and magnetostratigraphic correlations indicate the hemphillian blancan nalma boundary at guanajuato in central mexico is 4 7 4 8 ma and it pro

45 610 52 160 years of site and landscape occupation at nawarla gabarnmang arnhem land plateau northern australia we present bayesian modelling on a long sequence of radiocarbon ages from the archaeological site of nawarla gabarnmang central arnhem land plateau northern australia a horizon of wind borne sediments containing flaked stone artefacts and charcoal commencing 45 610 cal bp the young end of the modelled boundary age range which extends beyond the limit of the calibration curve with a median modelled age of 48 500 cal bp signals the onset of aeolian mobilisation of fine sands and silts across the landscape and re deposition within the site at a time synchronous with the first evidence of people this earliest cultural horizon stratigraphic unit 4 contains 509 stone artefacts and is marked by a contemporaneous sedimentary break from underlying culturally sterile sediments consisting of disintegrating roof fall and in situ sandstone and quartzite to overlying culturally rich wind blown sand the new radiocarbon ages and wind blown sediments together provide evidence for the commencement of noticeable landscape burning on the arnhem land plateau c 48 500 cal bp suggesting an intensification of landscape management practices at the summit of the arnhem land plateau some 10 000 e15 000 years after the lowest dense band of artefacts phase 2 at madjedbebe on the floodplains 90 km to the north these results have ramifications for the structure and timing of the spread of people across australia and the extinction of megafauna in sahul

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

palaeoenvironmental significance of diatom and vertebrate fossils from late cenozoic tectonic basins in west central mexico a review abstract pronounced lacustrine sedimentation developed in west central mexico during the late miocene between approximately 11 and 7 ma this was in response to tectonic extension associated with the initial emplacement of the late miocene substrata of the trans mexican volcanic belt climatic conditions in west central mexico during this interval were relatively warm and humid based on the widespread distribution of interpreted lacustrine beds following a latest miocene 8 0 5 4 ma stage of arid conditions and greatly reduced deposition of fine grained lacustrine sediments extensive east west oriented relatively deep perennial lakes ensued they mark the early pliocene 5 3 4 0 ma lower pliocene diatomites contain the same diatom species e g stephanodiscus carconensis and tertiarius aff baikalensis found in rocks of this age in the western united states the relatively warm and humid conditions that characterized this interval in central mexico coincide with a period of high latitude warming higher global sea level and a reduction in size of the antarctic ice sheets because the central american seaway persisted until at least the latest miocene it might have acted to increase precipitation in central mexico this could have continued into the earliest pliocene mexican pliocene mammalian faunas also support a savanna setting with moist and warm conditions prevailing at the time shallow lakes and fluvial conditions dominate after 4 0 ma until the end of pleistocene a combination of reduced precipitation due to general global cooling and drying as well as volcanic and tectonic processes are presumed to have been the cause for this mid pliocene reduction in lake size and extent in central mexico

reappraisal of sea level lowstand during the last glacial maximum observed in the bonaparte gulf sediments northwestern australia abstract during the last glacial maximum lgm ice volume reached a relative maximum and global temperature was lower than today understanding continental ice volume change requires accurate reconstruction of relative sea level but tectonic uplift and isostatic adjustment effects complicate many records using marine sediment cores from the bonaparte gulf in northwestern australia a so called far field tectonically stable site yokoyama et al 2000 reported that the lgm terminated abruptly at 19 ka with a rapid sea level rise 19 ka event their sea level reconstruction determined the age of the lgm termination but the timing of its inception remained less well constrained partly because the number of radiocarbon analyses was insufficient to clarify lgm duration here we return to the bonaparte gulf and present a new relative sea level that better constrains lgm duration with high resolution radiocarbon dating of a recently recovered marine sediment core water depth 120 m length 583 cm radiocarbon dating of 23 molluscs and 26 bulk organic matter samples together with total organic carbon total nitrogen and stable carbon isotopes provide a record of paleoenvironmental variability in response to sea level change our results indicate that the lgm sea level minimum occurred at 20 8 cal ka bp and the lgm duration was shorter than previously reported

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

regional geological setting of guanajuato silver gold deposits and quantitative petrophysical assessment of their hydrothermal alteration guanajuato mexico abstract geological setting of one of the world famous silver gold deposits type is presented the silver gold vein system occurs in the southeastern portion of the sierra de guanajuato which is a 100 km long n45 w trending mountain range in central mexico the rocks exposed in the sierra de guanajuato and its surroundings can be divided into four broad stratigraphic successions 1 the basal complex which includes mesozoic rocks and an early eocene granitic batholith 2 a thick 1000 m red bed sequence resting unconformably atop the basal complex which was deposited in the lapse between 49 and 36 ma 3 a thick faulted and tilted paleogene subaerial volcanic succession and 4 immediately north of sierra de guanajuato are exposed a widespread flat lying sand and gravel deposits accumulated in a continental basin these sediments contain fossil vertebrate faunas with ages between late clarendonian and blancan southeast of el bajio fault system sand and gravel deposits partially covered by basaltic andesites crop out a similar relation between gravel deposits and mafic lava flows is seen at the top of cerro el cubilete which is one of the highest point in sierra de guanajuato succession 1 experienced several shortening events during the cretaceous and paleocene whereas successions 2 thru 4 were extended in several deformation pulses during the cenozoic wall rock alteration changes in some petrophysical parameters were studied in the veta madre vein in the central part of the guanajuato mining district hydrothermally altered rocks were characterized by their variations in the following petrophysical characteristics 1 density 2 effective porosity 3 rapid volumetric saturation and 4 constant saturation among the petrophysical characteristics was observed that is important for exploration at guanajuato 1 the rock density tends to fall near the structures that present ore bodies at depth and having little change when no hydrothermal alteration is present 2 the effective porosity pefec of rocks suitable for mineralization increase their values 3 the rapid volumetric conditioned saturation a plays a big role when the hydrothermal fluids pass near the rocks with high values and produces mineralization 4 the constant saturation 1 b their values tend to increase in areas with mineralization samples of host rocks collected above known spikes such as las torres and sirena exhibit hydrothermal alteration with the following petrophysical characteristics density tends to decrease whereas porosity rapid volumetric and constant saturation increase the use of these petrophysical parameters may be a low cost technique to predict the presence of undiscovered orebodies in the guanajuato mining district and elsewhere where similar mineralization occurs

palaeoenvironmental dynamics and palaeolithic occupation at katoati thar desert india late pleistocene palaeoenvironments in the thar desert india located at the eastern extent of the saharo arabian desert belt have fluctuated considerably as a result of the varying range and intensity of the indian summer monsoon phases of widespread pleistocene aridity are well documented in the thar desert but research focusing on humid proxies is critical to examine how the region may have facilitated population expansions across southern asia at katoati located on the northeast margin of the thar desert the combination of field recording of sediment sections with detailed analyses micromorphology stable isotope loss on ignition magnetic susceptibility and x ray fluorescence from an archaeological site identify a series of hominin occupations during phases of enhanced humidity between 96 and 60 ka a gradient of humidity on the eastern margin of the thar desert during the late pleistocene is identified with the periodic humidity evident at katoati occurring more frequently and with longer duration towards the southern margin this uneven distribution of humidity in the thar desert is likely to have strongly influenced when and where hominin populations could expand into and across the region

thermoluminescence chronology of toronto area quaternary sediments and implications for the extent of the midcontinent ice sheet s we report direct dating by thermoluminescence tl methods of key quaternary stratigraphic horizons in the toronto area tl ages indicate that 1 most of the exposed sediments of the don formation at the sampled site were probably deposited during the closing phase of the sangamon interglacial 80 ka oxygen isotope stage 5a not the climatic optimum substage 5e 120 130 ka as generally supposed 2 overlying deltaic strata of the scarborough formation which accumulated in an ice dammed ancestral lake ontario were deposited between 60 and 50 ka early wisconsin oxygen isotope stage 4 3 the sunnybrook diamict overlying the scarborough formation was deposited in the middle wisconsin at 40 45 ka oxygen isotope stage 3 likely by glaciolacustrine processes rather than before 65 ka as previously supposed 4 sediments of the upper thorncliffe formation lying stratigraphically just beneath the last glacial maximum hallton till were deposited at 23 ka consistent with reliable 14 c dating thus the earliest wisconsin incursion of the proto laurentide ice sheet into the lake ontario basin as recorded by the scarborough formation probably did not take place until at least 60 ka and did not extend south and southwest of the toronto area until after 25 ka ice free conditions probably persisted over large areas of midcontinent north america from the end of the illinoian glaciation at 130 ka to the late wisconsin glacial maximum at 20 ka

blancan hemphillian land mammal ages and late cenozoic mammal dispersal events vertebrate fossils have produced a reliable and useful framework for interpreting geologic history during the cenozoic era and for unraveling the complex evolution of mammals this framework was formalized for north america in 1941 as the north american provincial land mammal ages wood et ai 1941 during the last 40 years that framework has been revised extended and calibrated so that land mammal ages are now the prime chronologie standard for terrestrial deposits of the cenozoic land mammal ages have been calibrated and resolved because of numerous studies relating mammal fossils and fossil sites to modern systematic analyses detailed biostratigraphic analyses new radiometric dating

large variations in the holocene marine radiocarbon reservoir effect reflect ocean circulation and climatic changes accurate radiocarbon dating of marine samples requires knowledge of the marine radiocarbon reservoir effect this effect for a particular site region is generally assumed constant through time when calibrating marine 14c ages however recent studies have shown large temporal variations of several hundred to a couple of thousand years in this effect for a number of regions during the late quaternary and holocene here we report marine radiocarbon reservoir correction r r for heron reef and moreton bay in southwestern sw pacific for the last 8 ka derived from 14c analysis of 230th dated corals most of our r r for the last 5 4 ka agree well with their modern value but large r r variability of 410 yr from trough to peak with possible decadal centennial fluctuations is evident for the period 5 4 8 ka the latter time interval also has significant variations with similar features in previously published r r values for other sites in the pacific including southern peru northern chile in southeastern se pacific the south china sea vanuatu and papua new guinea with the largest magnitude of 920 yr from se pacific the mechanisms for these large r r variations across the pacific during the mid holocene are complex processes involving 1 changes in the quantity and 14c content of upwelled waters in tropical east pacific tep frequency and intensity of ocean upwelling in the tep and contribution of subantarctic mode water to the upwelled waters which is influenced by the intensity and position of southern westerly winds and 2 variations in ocean circulation associated with climate change la nina el nino conditions intensity of easterly trade winds positions of the intertropical convergence zone and the south pacific convergence zone which control the spreading of the older upwelled surface waters in the tep to the western sites our results imply the need for employing temporal changes in r r values instead of constant modern values for age calibration of holocene marine samples not only for the sw pacific sites but also for other tropical and subtropical sites in the pacific

the early occupation of the eastern pilbara revisited new radiometric chronologies and archaeological results from newman rockshelter and newman orebody xxix abstract for over 30 years the radiometric chronologies of newman rockshelter and newman orebody xxix have been central to archaeological discussions on the pleistocene aboriginal occupation of the hamersley plateau and greater pilbara region until 2009 these two sites were heralded as having the oldest evidence of human occupation on the plateau dating to the last glacial maximum lgm 26 20 ka more recently however the excavations at several other rockshelters have shown that ancient aboriginal peoples occupied the hamersley plateau many thousands of years before the onset of the last glacial cycle when regional climatic conditions were wetter and more amenable this paper presents the results of our re excavation of both newman rockshelter and newman orebody xxix our research has resulted in the compilation and analysis of large lithic datasets for each of these sites and the construction of geo chronologies using modern radiometric techniques including ams radiocarbon dating and optically stimulated luminescence dating these new radiometric chronologies and artefact data indicate that both sites were occupied between 45 and 40 ka despite having significant early occupational evidence neither of the rockshelters present strong evidence for sustained or persistent site use during the lgm proper ca 23 19 ka however there is substantial evidence for more routine occupation of these localities during the terminal pleistocene and holocene

late pleistocene and early holocene exploitation of estuarine communities in northwestern australia this contribution synthesizes archaeological studies of human economies from the barrow montebello islands and uses the area s archaeological record to determine the effects of late pleistocene and early holocene sea level rise on regional coastlines at the height of the last glacial maximum lgm australia s north western coast extended much further west than the present day shoreline during subsequent sea level rise the gently prograding continental shelf was inundated and with it nearly all archaeological evidence for coastal occupation the barrow and montebello islands are one of the few exceptions as they corresponded to inland hinterland ranges during the lgm with the coastline lying some 50 km to their west evidence from all late pleistocene and holocene occupation phases of the barrow montebello islands demonstrate that foragers continued to visit the coast and engage in the exploitation of both terrestrial and marine environments during the late pleistocene when the shoreline was 10 15 km away coastal exploitation is seen through the presence of transportable estuarine and rocky shore gastropods by the early holocene when sea levels were within close proximity of the sites there is a marked increase in marine fauna including reef fish estuarine and reef shellfish crustaceans and estuarine crocodile together this suggests that the nearby muddy procumbent coastlines were productive as well as an important component of coastal and hinterland economies

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research