trace fossils biology and taphonomy 1990 special topics in palaeontology 3 280 pp e17 95 pbk e40 00 hbk unwin hyman london isbn 004445 6867 pbk 3035 hbk

glaciation and tectonics in an active intracratonic basin the late palaeozoic itarare group parana basin brazil the parana basin 1 600 000 km2 is the largest intracratonic basin in southern south america and contains a thick 1300 m permo carboniferous glacial succession the itarare group this paper describes over 1700 m of drill core recovered during recent exploration for oil and gas itarare group sediments consist of massive and stratified diamictites interbedded with massive and graded sandstones and massive and laminated mudstones facies are interpreted as the product of sediment gravity flows in a glacially influenced marine basin three stratigraphic formations can be defined across the basin each consisting of a lowermost sandstone rich member overlain by a diamictite rich member examination of itarare group rocks both in core and outcrop shows that depositional processes were influenced by active faulting and downslope resedimentation on relatively steep and unstable substrate slopes primary glacial deposits such as tillites and associated striated pavements occur along the present eastern outcrop belt which probably coincided with the eastern basin margin during deposition of the itarare group ice masses fringing the eastern southern african and western bolivian basin margins supplied sediment to the basin in the form of fluvio glacial deltas fans and floating ice tongues this sediment was then resedimented downslope as debris flows and turbidites both stratigraphic relationships and the regional distribution of facies types identify a clear pattern of basin subsidence and step wise expansion by outward faulting within late proterozoic mobile belts the position of successive basin margins can be related to specific lineament structures in the underlying basement asymmetric expansion of the parana basin occurred along the northern and southern basin margins during deposition of the itarare group this expansion probably reflects shallow crustal adjustments activated by collisional movements along the andean margin of south america during the hercynian orogeny

sequence stratigraphy of a lagoonal estuarine system an example from the lower permian rio bonito formation parana basin brazil abstract detailed stratigraphic analysis of the early permian artinskian kungurian succession of the intracratonic parana basin in southernmost brazil has revealed that the study region previously interpreted as formed by a barrier island system in a shallow wave dominated sea actually originated mainly in a mixed tide and wave influenced estuary setting four main depositional systems have been recognized alluvial fan fluvial dominated delta lagoonal estuary and barrier shoreface the regional correlation of the lithofacies within the different depositional systems has led to a high resolution stratigraphic framework with three third order depositional sequences sequence boundary sb1 marks the base of the permian succession above the crystalline basement sequence boundary sb2 is characterized by fluvial sediments overlying marine shales and sandstones sequence boundary 3 sb3 has a different signature reflecting differential subsidence some areas clearly experienced temporary regression and basinward shift of facies while in others the transgression rapidly reworked the regressive sediments and left only a thin veneer of pebbly sandstone the typical signature of a transgressive surface coinciding with a sequence boundary within depositional sequence 2 the main target of the study because it has economically important coal seams seven parasequences are recognized two forming the lowstand systems tract of the sequence four forming the transgressive systems tract and one parasequence forming the highstand systems tract two parasequence limits are erosional transgressive surfaces as indicated by the occurrence of a substrate controlled ichnofacies glossifungites and a veneer of intraclasts composed of nodules chert shell fragments and muddy rip up clasts the base level variations had a strong tectonic component as indicated by 1 the shift in shoreline configuration from east west to a north south direction after unconformity sb3 formation 2 the transgressive reworking of regressive sediments in the southern part of the study area indicating differential subsidence and consequent differential accommodation available for the sediments and 3 the angularity displayed by the strata adjacent to the sequence boundary sb3

shallow marine response to global climate change during the paleocene eocene thermal maximum salisbury embayment usa the paleocene eocene thermal maximum petm was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale here we examine the sediments flora and fauna from an expanded section at mattawoman creek billingsley road mcbr in maryland and explore the impact of warming at a nearshore shallow marine 30 100 m water depth site in the salisbury embayment observations indicate that at the onset of the petm the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input changes in microfossil biota suggest stratification of the water column and low oxygen bottom water conditions in the earliest eocene formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites this proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12c enriched co2 we conclude that the mcbr site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming

role of temperature and nutrients in extinction of turritelline gastropods cenozoic of the northwestern atlantic and northeastern pacific abstract turritelline gastropods mesogastropoda turritelline are common to abundant components in many fossil cretaceous cenozoic and recent marine benthic communities but the environmental factors affecting their evolution and extinction are poorly understood this is in large part because today they occur most abundantly in cooler waters associated with upwelling or other high nutrient conditions but thermal tolerances and preferences are unclear for extinct turritelline species turritellines were diverse and abundant throughout the new world for much of the cenozoic beginning in the early neogene through both extinction and range contraction however they started to disappear from higher latitudes on both atlantic and pacific coasts of north and central america the highest rate of extinction took place in the western atlantic in the plio pleistocene when almost all turritelline species in this area became extinct preliminary comparison of the available stratigraphic record suggests that this paleobiogeographic pattern is not an artefact of the record this biogeographic shift coincides with a postulated regional mass extinction among all marine mollusks in the western atlantic at around the same time causes for turritelline extinction however appear to be more complex than the decline in temperature that is cited most often as the probable cause of the western atlantic molluskan extinction event neogene turritellines in the western atlantic appear to have been adversely affected by collapse and or major reorganization of oceanic productivity associated with the formation of the isthmus of panama nutrients thus may have been more important than temperature change in controlling extinction probability in this group

cenozoic marine sedimentation and ice volume variation on the east antarctic craton recycled cretaceous and cenozoic marine microfossils have been recovered from samples of the pliocene sinus formation samples were collected from outcrops in the reedy beardmore and ferrar glacier areas of the transantarctic mountains between lat 77 and 86 s the glaciogene sediments contained diatoms foraminifera calcareous nannoplankton silicoflagellates radiolarians sponge spicules palynomorphs and ostracodes of late cretaceous paleocene eocene late oligocene late miocene and pliocene age this suggests the presence of open marine basins on the east antarctic craton during late mesozoic and cenozoic time the apparent absence of early oligocene and early through middle and earliest late miocene assemblages suggests either that marine regression exposed the basin floors or that ice filled the basins during these times the high elevation setting of sirius formation outcrops suggests one of two hypotheses for their origin 1 they are in situ pliocene glaciomarine deposits that were uplifted 1 750 2 500 m with the transantarctic mountains to their present elevation 2 the sirius formation deposits are a mixture of derived sediments stripped from sub ice intracratonic basins and subsequently redeposited by ice flowing up the inland slope of the transantarctic mountains we favor the second hypothesis with transport to sites sometime within the past 3 m y

a new stratigraphic framework built on u pb single zircon tims ages and implications for the timing of the penultimate icehouse parana basin brazil

foraminiferal distribution on the continental margin off nova scotia abstract q mode factor analysis of total foraminiferal abundance data living plus dead from 250 grab samples taken from the continental margin off nova scotia allows the determination of eight factor assemblages on the northeastern shelf an exclusively agglutinated assemblage dominated byadercotryma glomerata occupies both banks and basins central shelf basins contain a predominantly calcareous assemblage dominated byglobobulimina auriculata andnonionellina labradorica transitional between these two factor assemblages is an agglutinated assemblage dominated bysaccammina atlantica consistently present along the shelf edge is atrifarina angulosa assemblage in northeastern bays and a few samples near sable island an agglutinatedeggerella advena assemblage is found a relict and transport affected assemblage dominated byelphidium excavatum occurs in the southwestern approaches to emerald basin sandy gravelly areas of the inner shelf and outer bank regions are characterized by acibicides lobatulus assemblage the statistical relationships of these defined assemblages to various aspects of the marine environment depth temperature salinity percent gravel sand and mud were investigated through multiple regression techniques results indicate that the present foraminiferal distribution patterns off nova scotia are influenced by the prevailing watermass characters and substrate theadercotryma glomerata assemblage is influenced by the presence of cold 0 4 c low salinity waters 32 33 of arctic labrador current origin the central basin assemblage g auriculata is related to warmer 8 12 c more saline waters 35 of slope origin the transition between these two bottom waters is marked by the opportunisticsaccammina atlantica assemblage preferred substrate character possibly determines the occurrence of thecibicides lobatulus islandiella islandica andeggerella advena assemblages trifarina angulosa shows a significant relationship to salinity and depth although the surficial sediments on the nova scotian shelf are largely the product of reworking of glacial deposits during late glacial and early holocene times all but thee excavatum factor assemblage appear to be in equilibrium with the modern oceanographic regime

predation in the paleozoic gastropod like drillholes in devonian brachiopods middle devonian articulate brachiopods ludlowville and moscow formations hamilton group new york have external tapered holes with a central boss that are indistinguishable from drillholes of naticid gastropods that are known from the triassic and later drillholes are specific to prey ribbed shells were avoided and specific to sites on prey healed drillholes suggest penetration of live prey as many as 44 percent of the preferred prey are drilled indicating a level of predation that has been reported only from post paleozoic strata

a benthic foraminiferal record of middle to late pliocene 3 15 2 85 ma deep water change in the north atlantic abstract records of benthic foraminifera from north atlantic dsdp site 607 and hole 610a indicate changes in deep water conditions through the middle to late pliocene 3 15 to 2 85 ma quantitative analyses of modern associations in the north atlantic indicate that seven species fontbotia wuellerstorfi cibicidoides kullenbergi uvigerina peregrina nuttallides umboniferus melonis pompilioides globocassidulina subglobosa and epistominella exigua are useful for paleoenvironmental interpretation the western north atlantic basin site 607 was occupied by north atlantic deep water nadw until 2 88 ma at that time n umboniferus increased indicating an influx of southern ocean water sow the eastern north atlantic basin hole 610a was occupied by a relatively warm water mass possibly northeastern atlantic deep water neadw through 2 94 ma when sow more strongly influenced the site these interpretations are consistent with benthic 18o and 13c records from 607 and 610a raymo et al 1992 the results presented in this paper suggest that the north atlantic was strongly influenced by northern component deep water circulation until 2 90 2 95 ma after that there was a transition toward a glacially driven north atlantic circulation more strongly influenced by sow associated with the onset of northern hemisphere glaciation the circulation change follows the last significant sst and atmospheric warming prior to 2 6 ma

response of deep ocean circulation to initiation of northern hemisphere glaciation 3 2 ma carbon isotopic records from benthic foraminifera are used to map patterns of deep ocean circulation between 3 and 2 million years ago the interval when significant northern hemisphere glaciation began the 18o and 13c data from four atlantic sites 552 607 610 and 704 and one pacific site 677 show that global cooling over this interval was associated with increased suppression of north atlantic deep water nadw formation however the relative strength of nadw production was always greater than is observed during late pleistocene glaciations when extreme decreases in nadw are observed in the deep north atlantic our data indicate that an increase in the equator to pole temperature gradient associated with the onset of northern hemisphere glaciation did not intensify deepwater production in the north atlantic but rather the opposite occurred this is not unexpected as it is the warm high salinity characteristic rather than the low temperature of thermocline waters that is critical to the deepwater formation process in this region today

reconstructing late quaternary deep water masses in the eastern arctic ocean using benthonic ostracoda abstract the distribution of ostracoda in three long cores from the deep eastern arctic ocean was studied to determine the palaeoceanographical history of the eurasian basin during the late quaternary the samples for this study were obtained from the lomonosov ridge morris jesup rise and yermak plateau during the arctic 91 expedition ostracoda previously studied in coretops at the same sites as the present study have shown that individual species have a strong association with different water masses and bathymetry throughout the late quaternary cores exhibit ostracod rich layers separated by barren intervals on the basis of biostratigraphical isotopic and palaeomagnetic data the fossiliferous levels are interpreted as representing interglacial stages the twenty most significant species were selected for subsequent quantitative investigation using cluster and factor analyses in order to determine similarity and variance between the assemblages an additional statistical method employing modern analogues and the squared chord distance dissimilarity coefficient was utilised to compare the present late quaternary fossil samples with a modern arctic database the results reveal a major faunal division within the arctic ocean deep water aodw highly abundant and diverse assemblages within the cores were found to group and have good analogues with the recent bathyal depth 1000 2500 m upper aodw assemblages conversely assemblages with low abundance and diversity correlate well with abyssal depth 3000 m lower aodw assemblages the palaeoceanographical history is complicated by the influence of adjacent water masses such as canada basin deep water cbdw greenland sea deep water gsdw and most importantly arctic intermediate water aiw which all had an influence on the ostracod assemblages during the late quaternary an enhanced flow of warm saline aiw into the eurasian basin results in species rich upper aodw assemblages having good analogues down to 2750 m in the water column in contrast lower aodw assemblages influenced by cold well oxygenated gsdw give analogues at depths as shallow as 1000 m the faunal changes are the consequence of rapid climatic fluctuations in the eastern arctic ocean during the late quaternary that are intrinsically linked to palaeoceanographical alternations in warm and cold current inflow from adjacent basins

two bioerosion ichnofacies produced by early and late burial associated with sea level change in bioerosion as in trace fossils as a whole deeply emplaced structures have greater survival value than shallow structures that is to say tiering the relative depth to which rasping etching and boring organisms penetrate their substrate is of paramount importance for the preservation potential of individual trace fossils an entobia ichnofacies is established for trace fossil assemblages dominated by deep tier borings and arising from long term bioerosion such as occurs on sediment free submarine cliffs or hardgrounds a gnathichnus ichnofacies comprises assemblages containing all tiers including superficial sculptures produced by radulation that have very little preservation potential such assemblages occur in short term bioerosion situations as on shell surfaces and hardgrounds buried early by sedimentation

the prism pliocene palaeoclimate reconstruction time for a paradigm shift global palaeoclimate reconstructions have been invaluable to our understanding of the causes and effects of climate change but single temperature representations of the oceanic mixed layer for dat

a fossil record full of holes the phanerozoic history of drilling predation the evolutionary history of drilling predation despite a long and rich fossil record precambrian holocene contains a 120 m y gap late triassic early cretaceous drilled bivalve and brachiopod shells from jurassic deposits of hungary india and four localities documented in the literature indicate that drillers may have existed continuously throughout the mesozoic they may have been descendants of paleozoic predators unknown mesozoic carnivores or precursors of modern drillers a literature database suggests three major phases in the phanerozoic history of drilling predators 1 the paleozoic phase latest precambrian carboniferous dominated by rare to moderately frequent drillings in brachiopods and sessile echinoderms 2 the mesozoic phase permian early cretaceous with very rare or even facultative drillers that had little impact on marine benthic communities but nevertheless may have been present continuously and 3 the cenozoic phase late cretaceous holocene dominated by frequent gastropod drillings in mollusks

a quantitative micropaleontologic method for shallow marine peleoclimatology application to pliocene deposits of the western north atlantic ocean abstract a transfer function was developed to estimate summer and winter paleotemperatures for arctic to tropical regions of the western north atlantic ocean using fossil ostracode assemblages q mode factor analysis was run on ostracode assemblages from 100 modern bottom sediment samples from continental shelves of north america greenland and the caribbean using 59 ostracode taxa seven factors accounting for 80 of the variance define assemblages that correspond to frigid subfrigid cold temperate mild temperate warm temperate subtropical and tropical climatic zones multiple regression of the factor matrix against observed february and august bottom temperatures yielded an astracode transfer function with an accuracy of about 2 c the transfer function was used to reconstruct middle pliocene 3 5 3 0 ma shallow marine climates of the western north atlantic during the marine transgression that deposited the yorktown formation virginia and north carolina the duplin formation south and north carolina and the pinecrest beds florida middle pliocene paleowater temperatures in virginia averaged 19 c in august and 13 5 c in february about 5 c to 8 c warmer than at comparable depths off virginia today august and february water temperatures in north carolina were 23 c and 13 4 c in south carolina about 23 c and 13 5 c and in southern florida about 24 6 c and 15 4 c marine climates north of 35 n were warmer than today south of 35 n they were about the same or slightly cooler thermal gradients along the coast were generally not as steep as they are today the north atlantic transfer function can be applied to other shallow marine pliocene and pleistocene deposits of eastern north america

forested arctic evidence from north greenland shallow water marine sediments of the kap kabenhavn formation at lat 82 30 n perry land north greenland contain an abundance of well preserved remains of terrestrial vegetation and invertebrate fauna indicative of a mosaic of forest tundra environments having similarities to present conditions in labrador the presence of foraminifera faunas marine molluscs and one mammal species supported by studies of paleomagnetism and amino acid diagenesis suggests an age of 2 ma at the pliocene pleistocene transition at this time the arctic tree line was located 2500 km to the north of its present position in the northwest atlantic region and forest tundra vegetation existed in lowland areas bordering on an arctic ocean without perennial sea ice cover

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

micropaleontological evidence for increased meridional heat transport in the north atlantic ocean during the pliocene the middle pliocene approximately 3 million years ago has been identified as the last time the earth was significantly warmer than it was during the last interglacial and holocene a quantitative micropaleontological paleotemperature transect from equator to high latitudes in the north atlantic indicates that middle pliocene warmth involved increased meridional oceanic heat transport

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

a new planktic foraminifer transfer function for estimating pliocene holocene paleoceanographic conditions in the north atlantic abstract a new planktic foraminifer transfer function gsf18 related 5 north atlantic assemblages to winter and summer sea surface temperature gsf18 based on recombined and simplified core top census data preserves most environmental information and reproduces modern north atlantic conditions with approximately the same accuracy as previous transfer functions but can be more readily applied to faunal samples ranging in age from pliocene to holocene transfer function gsf18 has been applied to faunal data from deep sea drilling project hole 552a to produce a 2 5 m y sea surface temperature sst time series estimates show several periods between 2 3 and 4 6 ma during which mean sst s were both several degrees warmer and several degrees cooler than modern conditions between 2 9 and 4 0 ma sst was generally warmer than modern except for a 250 k y interval centered at 3 3 ma maximum sst with respect to modern conditions occurred after the cool interval near 3 1 ma when sst was approximately 3 6 c warmer than present conditions comparison of sst estimates with stable isotope data suggest that after peak warming at 3 1 ma there was an overall surface water cooling with concomitant build up of global ice volume culminating in northern hemisphere glaciation this event is also indicated by the presence of ice rafted detritus in 552a sediments at about 2 45 ma

extreme freshwater release during the late paleozoic gondwana deglaciation and its impact on coastal ecosystems abstractstrata in the paganzo tarija and parana basins of argentina and brazil provideevidence for reconstructing the effects of late paleozoic glacial retreat the depositionalenvironment of the transgressive and early highstand ne grained deposits has been con troversial with interpretations ranging from normal marine shelves to estuaries to lakes whereas their counterparts from shallow marine settings not in uenced by glaciation hostdiverse fully marine ichnofaunas these ne grained postglacial deposits are dominatedby nonspecialized grazing trails simple feeding traces arthropod trackways and shtrails they are typical of freshwater environments and represent examples of the mermia and scoyenia ichnofacies however the local presence of acritarchs indicates sporadicmarine in uence these observations suggest a new interpretation that freshwater con ditions in fjordlike settings across south america were widespread because gondwananbasins were overwhelmed by strong meltwater discharge issuing from melting of the con tinental ice masses keywords

multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and late quaternary shelf sediments northern canada abstract benthic foraminifera in surface sediments from northeastern canada and the beaufort shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth temperature and salinity factor analysis shows that 7 factor assemblages account for 92 of the variance between samples multiple linear regression shows that different factors are significantly related to water depth august bottom water temperature or salinity multiple correlation coefficients for depth temperature and salinity are 0 94 0 72 and 0 92 respectively labrador fjords contain arenaceous faunas dominated by eithersaccammina atlantica andreophax fusiformis or byeggerella advena regression analysis shows that thesaccammina reophax factor is most strongly related to salinity theeggerella factor is related to depth and temperature a fauna dominated bytrochammina nana andbuliminella elegantissima is correlated with warm deep water in davis strait calcareous assemblages dominated byelphidium excavatum orcassidulina reniforme are found in arctic bays and shelf areas these factor assemblages are strongly related to temperature and depth cassidulina is also related to salinity anislandiella helenae fauna on the inner labrador shelf is strongly correlated with depth and salinity anonionellina labradorica fauna in deep shelf basins is closely related to salinity the multiple regression model for the sea bed data estimates water depth august bottom water temperature and salinity within confidence limits of 67 m 1 3 c and 1 0 paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the labrador shelf paleo depth estimates obtained from the core data produce relative sea level curves which are similar in shape to theoretical curves for this region paleo salinity and temperature estimates for offshore core 12 show that the change from a postglacialnonionellina fauna to a late glaciale excavatum fauna is accompanied by a decrease of about 2 in salinity and 4 c in temperature paleoecological estimates for fjord core 111 show that the change from a modernsaccammina reophax fauna to a mid holocenei helenae fauna corresponds to a salinity increase of 3 5 and temperature increase of 1 2 c

age constraints of the glaciation in the parana basin evidence from new u pb dates the absence of absolute dating in glacial deposits of the parana basin prevents better understanding of the complete history of the late palaeozoic ice age in western gondwana and the climatic change that took place in the late carboniferous in this study new u pb radiometric ages date the topmost glacial deposits of the itarare group at 307 7 3 1 ma kasimovian moscovian and the base of post glacial deposits of the rio bonito formation at 298 8 1 9 ma ghzelian asselian correlation of glacial and post glacial deposits of the parana basin with other southwestern gondwana basins shows that the end of the late palaeozoic ice age is asynchronous supplementary material laser ablation inductively coupled plasma mass spectrometry u pb zircon data and methods for the ash sample of the itarare group and the tonstein sample of the rio bonito formation are available at https doi org 10 6084 m9 figshare c 3278273

temporal patterns in the efficiency of naticid gastropod predators during the cretaceous and cenozoic of the united states coastal plain abstract the hypothesis of escalation predicts that highly armored more escalated prey will be selectively eliminated at mass extinctions if recovery faunas were dominated by less escalated species a relative decrease in the defensive abilities of prey should follow mass extinctions we tested this hypothesis by examining two indices of the relative efficiency of drilling naticid gastropod predators and their molluscan prey the percent of drill holes that were incomplete and the percent of holes occurring in multiply bored shells both represent unsuccessful drilling attempts due to interruption of the drilling process by physical or biological factors including escape tactics of the prey excessive prey thickness or predator inefficiency if recovery faunas were more vulnerable to predation the incidence of incomplete or multiple drill holes should decline following mass extinctions the data do not support this hypothesis of a total of 16 comparisons across four extinction boundaries two showed a significant decrease in failed drilling following mass extinctions in accord with the hypothesis oligocene gastropods had fewer incomplete drill holes than did eocene gastropods and the frequency of multiply bored gastropod specimens was less in the pleistocene than in the pliocene two comparisons yielded a significant increase in failed drilling in the recovery fauna contrary to the hypothesis bivalve recovery faunas in the oligocene and miocene showed significantly greater proportions of multiply bored specimens than did their pre extinction counterparts no overall trend in unsuccessful drilling was apparent in the cretaceous through cenozoic data incomplete and multiple drilling were relatively rare in the cretaceous paleocene and most of the eocene 0 12 failed drilling was significantly more common during the oligocene up to 20 and returned to lower levels for most of the remainder of the cenozoic

a paleoclimatic review of southern south america during the late paleozoic a record from icehouse to extreme greenhouse conditions abstract this paper provides a review of the late mississippian to permian paleoclimatic history for southern south america based on lithologic indicators biostratigraphic information and chronostratigraphic data the region is divided into three major types of basins 1 eastern intraplate basins e g parana basin 2 western retroarc basins e g paganzo basin and 3 western arc related basins e g rio blanco basin four major types of paleoclimatic stages are recognized in these basins 1 glacial late visean early bashkirian 2 terminal glacial bashkirian earliest cisuralian 3 postglacial cisuralian early guadalupian and 4 semiarid arid late guadalupian lopingian the glacial stage began in the late visean and continued until the latest serpukhovian or early bashkirian in almost all of the basins in southern south america during the bashkirian earliest cisuralian terminal glacial stage glacial deposits disappeared almost completely in the western retroarc basins e g paganzo basin but glaciation persisted in the eastern basins e g parana and sauce grande basins a gradual climatic amelioration postglacial stage began to occur during the earliest permian when glacial deposits completely disappeared across all of south america during this interval glacial diamictites were replaced by thick coal beds in the parana basin while north south climatic belts began to be delineated in the western basins which were likely controlled by the distribution of mountain belts along the panthalassan margin of south america towards the late permian climatic belts became less evident and semiarid or arid conditions dominated in the southern south america basins eolian dunes playa lake deposits and mixed eolian fluvial sequences occur in the parana basin and in the western retroarc basins volcanism and volcaniclastic sedimentation dominated along the western margin of south america at that time the stratigraphic record obtained in southern south america supports a long duration transition from icehouse to extreme greenhouse conditions

marine plio pleistocene of iceland and problems of its correlation abstract the marine pliocene pleistocene sequence of iceland contains four main assemblages of mollusks 1 venerupis rhomboides et al 2 serripes groenlandicus et al 3 portlandia arctica et al and 4 recent species analysis of the stratigraphic distribution of 100 species shows that the percentage of extinct species in the assemblages decreases from 40 in the oldest to 4 8 in the youngest there is also a change from south boreal affinities in the oldest assemblage to north boreal in the youngest the molluskan assemblages of iceland can be correlated with pliocene pleistocene assemblages of england and north europe 1 coralline crag 2 red crag lower part of the icenian strata 3 upper part of the icenian cromerian strata the upper boundaries of the pliocene and eopleistocene are defined by paleomagnetic data and radiological dating the upper boundary of the pliocene presumably should be established in the basalts lying between the tjornes and the breidavik deposits by changes between the second and third mollusk assemblages and by the gilsa paleomagnetic event

crowded rosselia ichnofabric in the early devonian of brazil an example of strategic behavior abstract the occurrence of crowded rosselia ichnofabric in early devonian deposits of transition beds western gondwana parana basin southern brazil and the paleobiology and paleoecology of its potential tracemakers are discussed in this paper crowded rosselia ichnofabric has been recorded chiefly in cenozoic storm beds associated with high sedimentation rates on the inner shelf and is usually interpreted as resulting from opportunistic behavior of terebellid polychaetes rosselia is a common ichnotaxon in the archetypical cruziana ichnofacies developed preferentially in fair weather deposits formed in inner shelf settings during storm surges however this endobenthic community is strongly affected decimating those that are unable to escape new records presented herein reinforce the conclusion that short term colonization represented by crowded rosselia ichnofabric occurs essentially in erosive storm deposits of high sedimentation rates rather than being opportunistic the crowded rosselia ichnofabric appears to be the result of a strategic behavior developed by stress tolerant terebellid polychaetes in inner shelf zones during or just after storm surges this strategic behavior appeared during the early paleozoic and was adopted by terebellids from their earliest appearance

bioerosion in shells from the early permian rio bonito formation brazil taphonomic paleobiological and paleoecological implications abstract we report the occurrence of sponge borings in composite molds of heteropectinid shells from early permian marine siliciclastic deposits of the parana basin of southern brazil sponge borings are preserved mainly as chambers entobia and channels entobia and clionolithes three preservational variations of entobia are present morphologically equivalent to the alpha beta and gamma ontogenetic stages of clionid sponges this equivalence suggests that the ontogenetic behavior in clionid sponges remains the same since early permian times and points to a conservative evolutionary trend for this group the pattern of bioerosion and other taphonomic signatures indicate rapid shell burial due to frequent and energetic storm events that might have limited the time available for bioerosion activity the new findings improve the paleozoic record of entobia and clionolithes and indicate that sponge borings have potential to be preserved in ancient siliciclastic rocks