terrestrial fossils in the marine presumpscot formation implications for late wisconsinan paleoenvironments and isostatic rebound along the coast of maine investigation of terrestrially derived organic remains within the late glacial marine presumpscot formation near portland maine adds one new shrub species six moss species and representatives of six families of insects to the fossil biota of the deposit white spruce picea glauca dominates the plant macrofossil assemblage the dominant pollen type is also spruce the total biotic assemblage probably represents remnants of a forest floor litter layer eroded along a stream and subsequently deposited offshore three accelerator mass spectrometer ams dates on spruce needles and cones suggest rapid burial with marine regression from the area by ca 11 500 bp

the holocene record of lake levels of mansell pond central maine usa a palaeohydrological study of mansell pond a small 4 ha closed basin lake in central maine revealed distinct changes in lake levels throughout the holocene we examined the texture organic content and macrofossils of eight cores and obtained 29 radiocarbon dates on transitions between sedimentary units the water level fell between about 8000 14 c yr bp and 6000 14 c yr bp and remained low until after 5000 14 c yr bp the water level may have begun rising as early as 4750 14 c yr bp with the most rapid increase occurring from 3225 14 c yr bp to 2780 14 c yr bp this interpretation varies at some points from an earlier assessment of mansell pond s holocene lake levels that was based on pollen and charcoal evidence from a single core records of holocene lake levels from eastern canada the lake ontario region and southern new england are inconsistent with each other suggesting that the influence of dominant air masses has been highly localized in this region

smoothing and extrapolation of crustal stress orientation measurements the theory and mechanics of a statistical smoothing algorithm for estimating stress fields based on observed data are described incorporated into the algorithm are tunable parameters which allow the user to adjust the smoothness and fidelity of the fitted stress field in addition the user has the option of using robustness weights or to weight the predicted stress field by assigning quality ranks to each data point fitted stress fields can be displayed as either a gridded map axes of maximum or minimum horizontal stress are shown as short bars located at each point in an evenly spaced grid or as a stress trajectory map examples of predicted stress fields for southern california and western canada based on borehole elongation data are displayed as stress trajectory maps a predicted paleostress field for the spanish peaks intrusion complex in colorado based on vertical dike orientations is displayed as a gridded map the smoothing algorithm is not limited to the analysis of stress orientation data any data consisting of a set of undirected lines measured at discrete locations are appropriate for input possible candidates include strain data mineral or intersection lineations and lineaments

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

a reevaluation of the enigmatic permian synapsid watongia and of its stratigraphic significance the enigmatic synapsid watongia initially described on the basis of fragmentary remains from the chickasha formation of oklahoma as an early therapsid a gorgonopsian is redescribed and is shown to represent the largest known varanopid synapsid its assignment to the varanodontinae varanopidae synapsida is supported by several diagnostic features including a strongly recurved marginal dentition with both posterior and anterior unserrated cutting edges quadratojugal with two discrete superficial rami a large lateral tuberosity on the postorbital short deep excavations on the neural arches and a broad short radiale the presence in watongia of a posterolateral process of the frontal precludes therapsid or sphenacodontid affinities the previously described preparietal that provided the strongest evidence of therapsid affinities for watongia is shown to be based on misinterpreted skull fragments that were incorrectly assembled the presence of a varanopid in the chickasha formation is consiste

no gap in the middle permian record of terrestrial vertebrates during the permian tetrapods showed a major transition from basal synapsid dominated faunas in the first half to therapsid dominated faunas in the second the transition was significant in marking the beginning of richer and more complex communities a precursor to modern terrestrial ecosystems this changeover may have been gradual or abrupt but its study has been complicated by the postulated occurrence of a substantial hiatus in the fossil record termed olson9s gap which obscured the nature of the turnover new evidence from redating of key tetrapod bearing units of the american southwest and european russia confirms that there is no gap in the fossil record of permian tetrapods indeed evidence for substantial sampling bias in the permian tetrapod fossil record as a whole is queried

maximum horizontal stress orientations in the cooper basin australia implications for plate scale tectonics and local stress sources summary borehole breakouts and drilling induced tensile fractures ditfs were interpreted in 61 wells in the cooper basin indicating an average maximum horizontal stress orientation of 101 n a total of 890 borehole breakouts and 608 ditfs were interpreted in the cooper basin the approximately east west maximum horizontal stress orientation is consistent over much of the basin except in the patchawarra trough where maximum horizontal stress rotates to a northwest southeast orientation this rotation in maximum horizontal stress orientation is consistent with in situ stress data to the northwest of the cooper basin the stress field in the cooper basin appears to mark the apex of a major horseshoe shaped rotation in maximum horizontal stress direction across central eastern australia finite element modelling of the in situ stress field of the indo australian plate iap using a range of plate scale tectonic forces is able to match the regional maximum horizontal stress orientation over most of australia reasonably well including the mean east west maximum horizontal stress orientation in the cooper basin however plate boundary scale modelling does not adequately match the horseshoe shaped stress rotation across central eastern australia the average east west maximum horizontal stress orientation in the cooper basin indicates that stresses from tensional forces acting along the tonga kermadec subduction zone are not transmitted into the interior of the australian plate the majority of the tensional forces associated with the tonga kermadec subduction zone are most likely accommodated along the numerous spreading centres within the lau havre backarc basin a number of more localized stress anomalies have also been identified these cannot be explained by plate scale tectonic forces and are possibly a result of geological structure and or density contrasts locally perturbing the stress field

a late glacial transition from picea glauca to picea mariana in southern new england abstract picea is an important taxon in late glacial pollen records from eastern north america but little is known about which species of picea were present we apply a recently developed palynological method for discriminating the three picea species in eastern north america to three records from new england picea glauca was dominant at 14 500 14 000 cal yr bp followed by a transition to picea mariana between 14 000 and 13 500 cal yr bp comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the younger dryas chronozone the ecological changes of the late glacial interval were not a simple oscillation in the position of a single species range but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors including climate edaphic conditions and atmospheric co2 levels

the postglacial history of three picea species in new england usa abstract given the difficulty of separating the three picea species p glauca p mariana and p rubens white black and red spruce in the pollen record little is known about their unique histories in eastern north america following deglaciation here we report the first use of a classification tree analysis cart to distinguish pollen grains of these species it was successfully applied to fossil pollen from eight sites in maine and one in massachusetts we focused on the late glacial early holocene 14 000 to 8000 cal yr b p and the late holocene 1400 cal yr b p to present the two key periods since deglaciation when picea has been abundant in the region the result shows a shift from a picea forest of p glauca and p mariana in the late glacial to a forest of p rubens and p mariana in the late holocene the small number of p rubens grains identified from the late glacial early holocene samples picea 1000 to 500 cal yr b p was likely the first time since deglaciation that p rubens was abundant in the region

the reptile macroleter first vertebrate evidence for correlation of upper permian continental strata of north america and russia the spectacular evolutionary history of terrestrial vertebrates is uncharacteristically poorly documented between the paleozoic subequatorial exposures of the permo carboniferous of north america and europe and the much higher latitude upper permian deposits of central russia and southern africa we report here that the discovery of the reptile macroleter in oklahoma provides the first direct vertebrate evidence of biochronological correlation between continental sediments from the upper permian of north america and russia the presence of the reptile macroleter a member of a major group of upper permian amniotes known previously only from central russia in north america improves dramatically our understanding of this early phase of amniote evolution and also provides evidence of terrestrial tetrapod faunal interchange between north america and russia in late permian time

stress in the indo australian plate cloetingh s and wortel r 1986 stress in the ind austr ian plate in b johnson and a w bally editors intraplate deformation characteristics processes and causes tectonophysics 132 49 67 we modelled the state of stress in the indo australian plate in order to investigate quantitatively variations observed in tectonic style the numerical procedure incorporates the dependence of slab pull and ridge push on the age of the oceanic lithosphere estimates are presented for the average net resistive forces at the himalayan collision zone the suction force acting on the overriding indo australian plate segment at the tonga kermadec trench and the drag at the base of the lithosphere our modelhng shows a concen ation of compressive stresses of the order of 3 5 lcbar in the ninetyeast ridge area the effects of the compressive resistance associated with himalayan collision and subduction of young lithosphere off the northern part of the sunda arc are focused in this region the stress field as calculated gives a consistent explanation for the observed concentration of seismic activity stein and okal 1978 and significant deformation in the oceanic crust weissel et al 1980 mcadoo and sandwell 1985 in the area the calculated stress field in the area adjacent to the southeast and central india ridges is characterized by tension parallel to the spreading axis this explains the concentration of near ridge normal faulting seismicity with t axes subparaile1 to the spreading ridge in the indian ocean as recently observed by bergman et al 1984 and wiens and stein 1984 the regional stress field along the strike of the sunda arc varies from compression seaward of and parallel to the sumatra trench segment to tension perpendicular to the java flores segment this explains the selective occurrence of well developed grabens seaward off the java flores segment of the trench observed by hilde 1983 our modelling shows that the observed rotation of the stress field denham et al 1979 in the australian continent is mainly the consequence of its geographic position relative to the surrounding trench segments and the variations of the forces acting on the down going slab in each of these the state of compression in west and central australia is induced by the action of resistive forces at the himalayan and banda arc collision zones the joint occurrence of high levels of compression in the plate s interior and normal faulting seismicity in the near ridge areas is a transient feature unique to the present dynamic situation of the indo australian plate

discussion and reply the reptile macroleter first vertebrate evidence for correlation of upper permian continental strata of north america and russia discussion reisz and laurin 2001 1 documented the presence of the reptile macroleter in the chickasha formation of oklahoma and concluded that the chickasha formation belongs to the guadalupian and that it is equivalent in age to the late kazanian or early tatarian of the russian platform p

a review of the guadalupian middle permian global tetrapod fossil record abstract until recently the guadalupian middle permian tetrapod fossil record was known almost exclusively from the karoo basin of south africa and the cis urals region of russia limiting progress towards understanding global middle permian tetrapod biogeography recent work has shed light on several new or under explored guadalupian tetrapod bearing basins and we review and synthesize these findings here we also review changes to the international and russian guadalupian time scales and present updated biostratigraphic correlations for all of the basins discussed in general there are few tetrapod genera or species shared between mid permian basins a pattern starkly different from the generic cosmopolitanism seen during lopingian late permian times the parana basin of brazil has produced a unique fauna that combines typical south african and russian clades suggesting a pathway for faunal interchange between the northern and southern portions of pangea the dashankou fauna of china yields basal therapsids that suggest a northern pangean origin for this clade the sundyr assemblage of russia preserves a latest guadalupian fauna that seems to illustrate patterns of faunal turnover across the guadalupian lopingian boundary continued field work in the lesser known mid permian strata will facilitate testing hypotheses about the transition between early and middle permian faunas the end guadalupian extinction event pangean tetrapod biogeography and the origins of widespread late permian clades

the first half of tetrapod evolution sampling proxies and fossil record quality abstract the first half of tetrapod evolution witnessed substantial diversification of the clade and several major turnovers and mass extinctions in the time since their origin more than 380 myr ago to the beginning of the middle jurassic 175 myr ago tetrapods apparently diversified fitfully reaching their highest level in the middle permian and showing major diversity declines in the late moscovian early permian wordian lower wuchiapingian end permian lower anisian lower ladinian late triassic lower norian to upper rhaetian end triassic and early jurassic upper sinemurian lower pliensbachian of these diversity drops only the end permian and end triassic correspond to recognised mass extinctions and the late moscovian and early norian drops to other previously identified environmental crises the remainder could be real extinction or turnover events or partially artefacts of biased sampling there are strong correlations between formation counts and tetrapod palaeodiversity suggesting a sampling component in the raw data but the covariation is not uniform through the whole time span being poor from devonian to middle permian and better from late permian to early jurassic there is limited evidence for covariation between the tetrapod palaeodiversity time series and other putative sampling metrics such as specimen completeness numbers of publications map areas gap bounded sedimentary units rock volumes formations and fossil collections modelling by multiple correlations shows that formation count is generally the best explanatory model either on its own or combined with other sampling time series however it is not clear that formation count is independent of the palaeodiversity time series because rises and falls in both signals could reflect variations in original diversity or in preservation or in sampling

mapped plant macrofossil and pollen records of late quaternary vegetation change in eastern north america abstract macrofossil presence absence maps and isopoll maps in 3000 year intervals show how ranges and abundance maxima for 12 eastern north american tree and shrub taxa picea p glauca p mariana larix laricina abies balsamea tsuga canadensis pinus strobus p resinosa p banksiana betula papyrifera b alleghaniensis b series humiles have changed from the last glacial maximum to the present the macrofossil maps corroborate patterns shown by the isopoll maps and provide spatial detail and taxonomic resolution the macrofossils confirm the inference from pollen data that unglaciated southeastern north america was cooler during the last glacial maximum 18 and 15 ka than simulated by the cohmap experiments with the ncar ccm0 general circulation model the geographic distribution of macrofossil occurrences during the late glacial 12 and 9 ka indicate that migration lag of boreal species did not occur at regional to subcontinental scales and that pollen assemblages lacking modern analogs resulted from climate gradients lacking modern analogs early holocene 9 and 6 ka macrofossil maps show rapid northward expansion of tree species ranges into deglaciated regions the data also show modest contractions of northern range limits of temperate species and expansions of southern range limits of boreal species in response to cooling trends during the late holocene 3 and 0 ka comparison of modern macrofossil maps of nine of these taxa with corresponding range maps confirm that the macrofossils record the geographic ranges accurately comparison of the modern macrofossil maps with maps of tree growing stock volume shows that for some taxa abies tsuga macrofossil occurrences were most frequent in regions of maximum tree abundance comparison of modern isopoll maps with the modern range and growing stock volume maps indicate that in contrast to the macrofossil data the pollen data provide poorer resolution of range limits for most taxa but better indications of abundance maxima and minima within the ranges

a three plate kinematic model for lau basin opening 1 we present revised compilations of bathymetry magnetization acoustic imagery and seismicity data for the lau basin and surrounds we interpret these data to more precisely locate the plate boundaries in the region and to derive a three plate kinematic model for the opening of the lau basin during the brunhes chron our tectonic model includes the niuafo ou microplate which is separated from the australian plate along the peggy ridge lau extensional transform zone central lau spreading center and from the tongan plate along the newly discovered fonualei rift and spreading center our model shows that australia tonga plate motion between 15 5 s and 19 s is partitioned across the microplate and it resolves the former apparent conflict between geodetic versus seafloor spreading velocities regionally this implies that the angular rate of opening of the lau basin has been faster than that of the havre trough to the south and that the rapid current rates of pacific subduction at the tonga trench 240 mm yr at 16 s have been sustained for at least 0 78 m y

structural evolution of the permian triassic cooper basin australia relation to hydrocarbon trap styles the structural and depositional history of the cooper basin in eastern central australia has revealed that the basin is a mildly compressional structural depression controlled by northwest trending and northeast trending pre permian basement features pronounced pre permian compressions are indicated by northeast trending major structures the gidgealpa merrimelia innamincka and murteree nappacoongee trends detailed chronostratigraphic facies analysis with closely spaced palynological control of the patchawarra formation revealed that two pronounced phases of uplift occurred during the sakmarian the major intrabasin highs were rejuvenated during these tectonic events as documented by crestal unconformities middle and upper patchawarra unconformities evidence of each event is dominantly tectonic in character with similar depositional patterns over these highs related to each event these events are also recognizable in midflank areas and basin margins with contemporaneous deposition in deeper parts of the basin results from this research show potential for future hydrocarbon discoveries within structural stratigraphic and structural stratigraphic traps in the cooper basin various trap styles are closely associated with faults unconformities and lateral facies changes lowside fault closures onlap plays and unconformity traps are expected to be well copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 22 1995 revised manuscript received august 6 1996 final acceptance november 12 1996 2geological survey of western australia 100 plain street east perth wa australia 6004 e mail n apak dme wa gov au 3national centre for petroleum geology and geophysics ncpgg university of adelaide thebarton campus university of adelaide sa 5005 australia 4santos ltd 101 grenfell street adelaide sa 7000 australia the authors wish to thank the cooper basin consortium group of companies for permission to publish this paper the drafting staffs at santos ltd and geological survey of western australia gswa are sincerely thanked for their efforts in preparing figures this paper is dedicated to the memory of bill stuart

heleosuchus an enigmatic diapsid reptile from the late permian or early triassic of southern africa the primitive diapsid reptile heleosuchus griesbachi from the late permian or early triassic of southern africa is redescribed on the basis of a new cast made from the type specimen few diagnostic features of the skeleton are preserved making it difficult to establish specific affinities no characters are known that are uniquely shared with archosauromorphs in common with lepidosauromorphs but in contrast with stem diapsids cervical vertebrae 3 5 are shorter than the anterior trunk vertebrae and the transverse processes are relatively short heleosuchus may be a member of the eosuchia or an otherwise unrecognized lineage of primitive lepidosauromorphs the possibility that this specimen shows thyroid fenestration of the pelvis and a shortened and or hooked fifth metatarsal cannot be unequivocally established

permian tetrapod extinction events abstract four substantial tetrapod extinctions have been identified during the permian but only one of these is an apparent mass extinction analyses of global compilations of the family level diversity of permian tetrapods have been confounded by incorrect and compiled correlations instead analyzing diversity patterns at the genus level in best sections identifies only one apparent mass extinction of permian tetrapods much evolutionary turnover took place among tetrapods during the latter part of the early permian and had been identified as a single mass extinction at the artinskian kungurian boundary however the only stratigraphically dense tetrapod record of the late early permian from the southwestern usa indicates a succession of extinctions spread out from redtankian through littlecrontonian kungurian time not a single mass extinction olson s gap remains a hiatus in the global record of permian tetrapods equivalent to part of the kungurian roadian across the gap eupelycosaur dominated assemblages were replaced by therapsid dominated assemblages but the claim that this is associated with a mass extinction olson s extinction has been based on compressing all of the extinctions of the redtankian littlecrotonian and olson s gap into one event recognition of olson s gap does not preclude the possibility of an extinction at the early middle permian boundary olson s extinction however the gap in the tetrapod fossil record makes it impossible to establish the magnitude precise timing and structure of the extinctions that took place across olson s gap the only permian mass extinction of tetrapods is the dinocephalian extinction event during the gamkan near the end of the guadalupian which saw the total extinction of dinocephalians and major diversity drop in therocephalians in the karoo basin of south africa this extinction is the loss of at least 64 of generic diversity the changeover from dinocephalian assemblages to assemblages without dinocephalians in other parts of permian pangea suggests that the dinocephalian extinction event was a global event the late permian tetrapod extinctions are older than the end permian marine extinctions furthermore the magnitude of the diversity drop and ecological severity of the end permian tetrapod extinctions have been greatly overstated best sections analysis in the karoo basin indicates a stepwise late permian tetrapod extinction during deposition of the upper dicynodon assemblage zone that took at least 250 000 and perhaps more than a million years the culmination of this stepwise extinction across the highest occurrence of dicynodon boundary of platbergian and lootsbergian land vertebrate faunachrons is a loss of genera not much above an inferred background extinction rate of permian tetrapod genera and resembles the amount of turnover seen at several other boundaries of permian and triassic land vertebrate faunachrons the case for coeval land plant insect and tetrapod extinctions during the permian is a weak one the first coeval marine and nonmarine mass extinctions of the phanerozoic were likely the end guadalupian extinction climate change notably greenhouse climates may have driven permian tetrapod extinctions but that hypothesized relationship needs better documentation

associated terrestrial and marine fossils in the late glacial presumpscot formation southern maine usa and the marine reservoir effect on radiocarbon ages article i nfo excavations in the late glacial presumpscot formation at portland maine uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit buds of populus balsamifera balsam poplar occurred with twigs of picea glauca white spruce in the presumpscot clay tree rings in picea logs indicate that the trees all died during winter dormancy in the same year ring widths show patterns of variation indicating responses to environmental changes fossil mosses and insects represent a variety of species and wet to dry microsites the late glacial environment at the site was similar to that of today s maine coast radiocarbon ages of 14 tree samples are 11 907 31 to 11 650 50 14 c yr bp wiggle

late holocene climate changes in eastern north america estimated from pollen data well dated pollen profiles from six sites from maine to minnesota record vegetation changes indicative of summer temperature and annual precipitation variations over the past 2000 yr laminations in the sediment provide accurate time control multiple regression techniques were used to calculate calibration functions from a spatial network of modern pollen and climate data when applied to the six pollen diagrams these calibration functions yielded estimates that show a long term trend toward lower summer temperature superimposed on this long term trend are short term fluctuations that are frequently in phase at the sites departures from the long term cooling trend are positive around 1500 yr ago indicating relative warmth and negative between 200 and 500 yr ago indicating relative cold annual precipitation showed a slight increase at several sites during the past 1000 yr relative to the previous 1000 yr

late glacial and early holocene landscapes in northern new england and adjacent areas of canada abstract the landscapes of northern new england and adjacent areas of canada changed greatly between 14 000 and 9000 yr b p deglaciation occurred sea levels and shorelines shifted and a vegetational transition from tundra to closed forest took place data from 51 14 c dated sites from a range of elevations were used to map ice and sea positions physiognomic vegetational zones and the spread of individual tree taxa in the region a continuum of tundra woodland forest passed northeastward and northward without major hesitation or reversal an increased rate of progression from 11 000 to 10 000 yr b p suggests a more rapid warming than in the prior 2000 3000 yr elevational gradients controlled the patterns of deglaciation and vegetational change the earliest spread of tree taxa was via the lowlands of southern vermont and new hampshire and along a coastal corridor in maine only after 12 000 yr b p did the taxa spread northward through the rest of the area different tree species entered the southern part of the area at different times and continued their spread at different rates the approximate order of arrival follows poplars 13 000 12 000 yr b p in the south spruces paper birch and jack pine followed by balsam fir and larch and possibly ironwood ash and elm and somewhat later by oak maple white pine and finally hemlock 10 000 9000 yr b p in the south