209 research outputs found
âCoal Age Galapagosâ: Joggins and the Lions of Nineteenth Century Geology
The celebrated coastal section at Joggins, Nova Scotia, has played a seminal role in the development of the Earth Sciences, ïŹguring in the careers of such lions of Nineteenth Century science as Lyell, Dawson, Darwin, Logan, Marsh, Gesner, Agassiz, Wyman and Owen, among others. The story that unfolds is not only one of scientiïŹc discovery, but one of enlightening interactions between the players that brings to life these personalities, their debates and, for some, their personal agendas. The âmarvellous chapter of the big volumeâ of Earthâs history recorded in the sea cliffs at Joggins served as a âCoal Age Galapagosâ for Lyell, Darwin, Dawson and others, furthering their case for geological and evolutionary principles that continue to inform scientiïŹc and popular views today. Coincidental with Lyellâs appearance on the scene, Logan undertook at Joggins one of the ïŹrst ïŹeld projects of the Geological Survey of Canada. Against the backdrop of advancing scientiïŹc thought and positions, a penny opera of professional one-upmanship was played out. Gesner sought reprimand of Lyell from Murchison, President of the Geological Society for misleading Nova Scotiaâs geologists; Owen, who earlier coined the word âdinosaurâ, beat Lyell and Dawson in naming their own discovery; while a young O.C. Marsh, presaging his intensely competitive dinosaur battles with Edward Cope, arrived at Joggins from Yale hot on Lyell and Dawsonâs trail, only to be duped by a worldly traveller ready to oblige his desire for fame. Above all others, the work of Dawson in describing the fossil record and its ecological context established a lasting legacy of relevance for the Joggins cliffs.
RĂSUMĂ
Le cĂ©lĂšbre secteur cĂŽtier de Joggins, en Nouvelle-Ăcosse, a jouĂ© un rĂŽle majeur dans lâessor des sciences de la terre : il ïŹgure parmi les carriĂšres de plusieurs personnages scientiïŹques du 19e siĂšcle, tels que Lyell, Dawson, Darwin, Logan, Marsh, Gesner, Agassiz, Wyman et Owen, entre autres. Lâhistoire des lieux ne se limite pas Ă une dĂ©couverte scientiïŹque; elle relate des interactions instructives entre les protagonistes mettant au jour ces personnalitĂ©s, leurs dĂ©bats et, dans certains cas, leurs prioritĂ©s personnelles. Le « merveilleux chapitre du grand volume » de lâhistoire de la terre, enregistrĂ© dans les falaises de Joggins, a constituĂ© un « genre de Galapagos de lâĂąge du charbon » pour Lyell, Darwin, Dawson et dâautres : il a soutenu les principes gĂ©ologiques et les principes de lâĂ©volution quâils avançaient et sur lesquels continuent de sâappuyer aujourdâhui les opinions scientiïŹques et populaires. En mĂȘme temps que Lyell apparaissait sur la scĂšne, Logan entreprenait Ă Joggins lâun des premiers projets de la Commission gĂ©ologique du Canada sur le terrain. Avec le dĂ©sir de faire progresser la pensĂ©e et les positions scientiïŹques en toile de fond, un opĂ©ra aux nombreux rebondissements sâest alors jouĂ© entre chercheurs professionnels. Gesner a demandĂ© Ă Murchison, prĂ©sident de la SociĂ©tĂ© gĂ©ologique, que Lyell soit rĂ©primandĂ© pour avoir induit en erreur les gĂ©ologues de la Nouvelle-Ăcosse. Owen, qui avait antĂ©rieurement avancĂ© le terme de « dinosaure », a battu Lyell et Dawson en baptisant leur propre dĂ©couverte. Cependant, un jeune O. C. Marsh, pressentant ses luttes profondes intensĂ©ment compĂ©titives avec Edward Cope, arrivait Ă Joggins en provenance de Yale, tout enthousiaste de sâengager dans le sillage de Lyell et de Dawson, mais seulement pour ĂȘtre dupĂ© par un voyageur dâexpĂ©rience prĂȘt Ă se plier Ă son dĂ©sir de cĂ©lĂ©britĂ©. Ămergeant au-dessus de tous les autres, les travaux rĂ©alisĂ©s par Dawson pour dĂ©crire les fossiles prĂ©sents et leur contexte Ă©cologique ont implantĂ© un hĂ©ritage durable et pertinent par rapport aux falaises de Joggins.
Traduit par la redaction
Sir William Dawson (1820â1899): a very modern paleobotanist
Sir William Dawson was one of Canadaâs most influential Nineteenth Century geologists. Although a lifelong opponent of the concept of evolution, a stance that resulted in him being sidelined by the scientific community, he made enormous contributions to Pennsylvanian paleobotany, especially at the Joggins fossil cliffs of Nova Scotia. Key to Dawsonâs success was his recognition of the importance of a field-based research program, in which fossil plants could be observed in their precise geological context over a sustained period of time. Uniquely trained as both geologist and botanist, he was skilled in the microscopic analysis of permineralized plant anatomy, and appreciated the enormous potential of fossil charcoal as an untapped source of systematic information. Arguably his most extraordinary insights came in the field of plant taphonomy, in which studies of modern sedimentary processes and environments were used to interpret the rock record. His analysis of fossil plants in their sedimentary context allowed Pennsylvanian coal swamp communities, dominated by lycopsids and calamiteans, to be distinguished from the coniferopsid forests, which occupied mountainous regions further inland. The lasting significance of Dawsonâs paleobotanical work is emphasized by many recent papers concerning the Pennsylvanian coal measures of Atlantic Canada, which have either directly built on research topics that Dawson initiated, or have confirmed hypotheses that Dawson framed. Until recent times, the discipline of paleobotany has been dominated by systematic fossil plant description with little or no reference to geological context. By virtue of his distinctively holistic approach, synthesizing all available geological and botanical data, Dawson is marked out from his contemporaries. His methodology does not appear old-fashioned even today, and it is therefore with justification that we describe him as a very modern paleobotanist.
Resumé
Sir William Dawson a Ă©tĂ© lâun des gĂ©ologues les plus influents du 19e siĂšcle au Canada. MĂȘme sâil sâest opposĂ© toute sa vie au concept de lâĂ©volution, une position qui a amenĂ© le milieu scientifique Ă lâignorer, il a Ă©normĂ©ment contribuĂ© Ă la palĂ©obotanique pennsylvanienne, spĂ©cialement dans les falaises fossilifĂšres de Joggins de la Nouvelle-Ăcosse. La clĂ© du succĂšs de Dawson rĂ©side dans le fait quâil avait reconnu lâimportance dâun programme de recherche sur le terrain prĂ©voyant lâobservation des plantes fossiles dans leur milieu gĂ©ologique particulier pendant une pĂ©riode de temps prolongĂ©e. GrĂące Ă sa formation unique de gĂ©ologue et de botaniste, il possĂ©dait la compĂ©tence voulue pour rĂ©aliser une analyse microscopique de lâanatomie des plantes perminĂ©ralisĂ©es et il comprenait le potentiel Ă©norme du charbon de bois fossile comme source inexploitĂ©e de donnĂ©es systĂ©matiques. On pourrait soutenir que ses idĂ©es les plus extraordinaires se sont manifestĂ©es dans le domaine de la taphonomie vĂ©gĂ©tale, dans lequel des Ă©tudes dâenvironnements et de processus sĂ©dimentaires modernes ont servi Ă interprĂ©ter des antĂ©cĂ©dents lithologiques. Ses analyses de plantes fossiles dans leur contexte sĂ©dimentaire ont permis de distinguer les communautĂ©s des marĂ©cages houillers pennsylvaniens, dans lesquels prĂ©dominent les lycopsides et les calamites, des forĂȘts conifĂ©ropsides, qui occupaient les rĂ©gions montagneuses plus Ă lâintĂ©rieur des terres. De nombreuses communications rĂ©centes au sujet des couches houillĂšres pennsylvaniennes des provinces de lâAtlantique, qui sâappuient directement sur des sujets de recherches amorcĂ©es par Dawson ou ayant confirmĂ© des hypothĂšses formulĂ©es par Dawson, mettent en relief lâimportance durable des travaux palĂ©obotaniques de Dawson. La discipline de la palĂ©obotanique a jusquâĂ tout rĂ©cemment Ă©tĂ© dominĂ©e par des descriptions systĂ©matiques de plantes fossiles Ă©voquant Ă peine ou nâĂ©voquant pas du tout le contexte gĂ©ologique. Dawson sâest dĂ©marquĂ© de ses contemporains au moyen de son approche nettement holistique en rĂ©alisant une synthĂšse de toutes les donnĂ©es gĂ©ologiques et botaniques accessibles. Sa mĂ©thode de travail ne semble pas rĂ©trograde, mĂȘme aujourdâhui, et il est par consĂ©quent tout Ă fait justifiĂ© que nous le dĂ©crivions en tant que palĂ©obotaniste trĂšs moderne
On the discovery of tetrapod trackways from Permo-Carboniferous redbeds of Prince Edward Island and their biostratigraphic signiïŹcance
The ïŹrst fossil tetrapod footprints that were discovered on Prince Edward Island, and which were previously undescribed, are small reptilian trackways assignable to the ichnogenera Notalacerta andGilmoreichnus. Their closest zoological correlatives are small, Permo-Carboniferous "stem-reptiles" of the families Protorothyrididae and Captorhinidae in the suborder Captorhinomorpha, and pelycosauran reptiles, possibly of the Ophiacodontidae. Reptiles of this type are rare to unrepresented in the skeletal fauna of the province. The biochronology of the track-bearing bed, combined with terrestrial vertebrate, palynological and macroïŹoral records, suggest that the host Pictou Group redbeds on Prince Edward Island young from late Stephanian (Pennsylvanian) at Malpeque Bay to early Permian in the north. The combined discoveries of tetrapod footprints and trackways from these Permo-Carboniferous redbeds suggests that the record is potentially extensive. Now included in this record is the youngest known occurrence of the ichno-genus Notalacerta.
RĂSUMĂ
Les premiĂšres empreintes de fossiles de tĂ©trapodes dĂ©couvertes sur l'Ăle-du-Prince-Ădouard, et prĂ©cĂ©demment non dĂ©crites, sont des traces d'un petit reptile qu'on peut rattacher aux ichnogenres Notalacerta et Gilmoreichnus. Leurs parents gĂ©ologiques les plus proches sont les petits " reptiles-tiges » permocarbonifĂšres des familles des protorothyridides et des captorhinides du sous-ordre des captorhinomorphes, ainsi que les reptiles pĂ©licosauriens, possiblement les ophiacodontides. Les reptiles de ce type sont rares sinon absents au sein de la faune squelettique de la province. La biochronologie des strates renfermant des traces conjuguĂ©e aux relevĂ©s de vertĂ©brĂ©s terrestres et aux relevĂ©s palynologiques et macroïŹoraux laisse supposer que les couches rouges hĂŽtes du groupe de Pictou, sur l'Ăle-du-Prince-Ădouard, remontent Ă la pĂ©riode du StĂ©phanien tardif (Pennsylvanien), dans la baie Malpeque, au Permien prĂ©coce, dans le nord. Les dĂ©couvertes combinĂ©es d'empreintes et de traces de tĂ©trapodes des couches rouges permocarbonifĂšres semblent indiquer que la quantitĂ© d'enregistrements pourrait ĂȘtre vaste. Ces enregistrements comprennent dĂ©sormais la manifestation la plus rĂ©cente connue de l'ichnogenre Notalacerta
[Traduit par la rédaction.
The Canadian Federation of Earth Sciences Scientific Statement on Climate Change â Its Impacts in Canada, and the Critical Role of Earth Scientists in Mitigation and Adaptation
The Canadian Federation of Earth Sciences (CFES) has issued this statement to summarize the science, effects, and implications of climate change. We highlight the role of Earth scientists in documenting and mitigating climate change, and in managing and adapting to its consequences in Canada. CFES is the coordinated voice of Canadaâs Earth Sciences community with 14 member organizations representing some 15,000 geoscientists. Our members are drawn from academia, industry, education, and government. The mission of CFES is to ensure decision makers and the public understand the contributions of Earth Science to Canadian society and the economy. Climate change has become a national and global priority for all levels of government. The geological record shows us that the global climate has changed throughout Earthâs history, but the current rates of change are almost unprecedented. Over the last 70 years, levels of common greenhouse gases (GHGs) in the atmosphere have steadily increased. Carbon dioxide (CO2) concentration is now 418 parts per million â its highest of the last three million years. The chemical (isotopic) composition of carbon in the atmosphere indicates the increase in GHGs is due to burning fossil fuels. GHGs absorb energy emitted from Earthâs surface and re-radiate it back, warming the lower levels of the atmosphere. Climatic adjustments that have recently occurred are, in practical terms, irreversible, but further change can be mitigated by lowering emissions of GHGs. Climate change is amplified by three important Earth system processes and effects. First, as the climate warms evaporation increases, raising atmospheric concentrations of water vapour, itself a GHG â and adding to warming. Second, loss of ice cover from the polar ice sheets and glaciers exposes larger areas of land and open water â leading to greater absorption of heat from the sun. Third, thawing of near-surface permafrost releases additional GHGs (primarily CO2 and methane) during decay of organic matter previously preserved frozen in the ground. Some impacts of climate change are incremental and steadily occurring, such as melting of glaciers and ice sheets, with consequent sea level rise. Others are intermittent, such as extreme weather events, like hurricanes â but are becoming more frequent. Summer water shortages are increasingly common in western Canada as mountain snowpacks melt earlier and summer river flows decline. In northern Canada, warming and thawing of near-surface permafrost has led to deterioration of infrastructure and increased costs for buildings that now require chilled foundations. Other consequences of unchecked climate change include increased coastal erosion, increases in the number and size of wildfires, and reduction in winter road access to isolated northern communities. Reductions in net GHG emissions are urgently required to mitigate the many effects of further climate change. Industrial and public works development projects must now assess the effects of climate change in their planning, design, and management. Cities, municipalities, and rural communities need to plan new residential development carefully to avoid enhanced risk of flooding, coastal erosion, or wildfire. Earth Science knowledge and expertise is integral to exploration and development of new metals and Earth materials required for a carbon-neutral future, and in the capture and storage of CO2 within the Earth. Earth Science is also central to societyâs adaptation to new climatic regimes and reduction of risks. This includes anticipation, assessment, and management of extreme events, development of new standards and guidelines for geotechnical and engineering practice, and revision to regulations that consider climate change. Geoscientists also have an important role in the education of students and the public on the reasons for necessary action. Canada is uniquely positioned with its strong global geoscientific leadership, its vast landmass, and its northern terrain to effectively leverage research activities around climate change. Geoscience tools and geoscientistsâ skills will be integral to Canadaâs preparation for climate change.La FĂ©dĂ©ration canadienne des sciences de la Terre (FCST) a publiĂ© ce communiquĂ© pour rĂ©sumer la science, les effets et les implications des changements climatiques. Nous soulignons le rĂŽle des scientifiques en science de la Terre dans la documentation et l'attĂ©nuation des changements climatiques, ainsi que dans la gestion de leurs consĂ©quences et la crĂ©ation de mesures d'adaptation au Canada. La FCST est la voix coordonnĂ©e de la communautĂ© canadienne des sciences de la Terre avec 14 organisations membres reprĂ©sentant environ 15 000 gĂ©oscientifiques. Nos membres sont issus du milieu universitaire, de l'industrie, de l'Ă©ducation et du gouvernement. La mission de la FCST est de s'assurer que les dĂ©cideurs et le public comprennent les contributions des sciences de la Terre Ă la sociĂ©tĂ© canadienne et Ă l'Ă©conomie. Les changements climatiques sont devenus une prioritĂ© nationale et mondiale Ă tous les niveaux de gouvernement. Les archives gĂ©ologiques nous montrent que le climat mondial a changĂ© tout au long de l'histoire de la Terre, mais les taux de changement actuels sont presque sans prĂ©cĂ©dent. Au cours des 70 derniĂšres annĂ©es, les niveaux de gaz Ă effet de serre (GES) communs dans l'atmosphĂšre n'ont cessĂ© d'augmenter. La concentration de dioxyde de carbone (CO2) est maintenant de 418 parties par million - son plus haut niveau des trois derniers millions d'annĂ©es. La composition chimique (isotopique) du carbone dans l'atmosphĂšre indique que l'augmentation des GES est due Ă la combustion de combustibles fossiles. Les GES absorbent l'Ă©nergie Ă©mise par la surface de la Terre et la rĂ©flĂ©chissent, rĂ©chauffant les niveaux infĂ©rieurs de l'atmosphĂšre. Les modifications climatiques qui se sont produits rĂ©cemment sont, concrĂštement, irrĂ©versibles, mais les changements additionnels peuvent ĂȘtre attĂ©nuĂ©s en rĂ©duisant les Ă©missions de GES. Les changements climatiques sont amplifiĂ©s par trois processus et effets importants du systĂšme terrestre. PremiĂšrement, Ă mesure que le climat se rĂ©chauffe, l'Ă©vaporation augmente, ce qui augmente les concentrations atmosphĂ©riques de vapeur d'eau, elle-mĂȘme un GES, et contribue au rĂ©chauffement. DeuxiĂšmement, la perte de la couverture de glace des calottes glaciaires polaires et des glaciers expose de plus grandes superficies de terre et d'eau libre, ce qui entraĂźne une plus grande absorption de la chaleur du soleil. TroisiĂšmement, le dĂ©gel du pergĂ©lisol proche de la surface libĂšre des GES supplĂ©mentaires (principalement du CO2 et du mĂ©thane) lors de la dĂ©composition de la matiĂšre organique jusquâalors prĂ©servĂ©e gelĂ©e dans le sol. Certains impacts des changements climatiques sont progressifs et se produisent rĂ©guliĂšrement, comme la fonte des glaciers et des calottes glaciaires, avec pour consĂ©quence une Ă©lĂ©vation du niveau de la mer. D'autres sont intermittents, comme les Ă©vĂ©nements mĂ©tĂ©orologiques extrĂȘmes, tels que les ouragans, mais deviennent de plus en plus frĂ©quents. Les pĂ©nuries d'eau en Ă©tĂ© sont de plus en plus courantes dans l'ouest du Canada, car le manteau neigeux des montagnes fond plus tĂŽt et le dĂ©bit des riviĂšres en Ă©tĂ© diminue. Dans le nord du Canada, le rĂ©chauffement et le dĂ©gel du pergĂ©lisol proche de la surface ont entraĂźnĂ© une dĂ©tĂ©rioration des infrastructures et une augmentation des coĂ»ts des bĂątiments qui nĂ©cessitent maintenant des fondations rĂ©frigĂ©rĂ©es. Les autres consĂ©quences des changements climatiques incontrĂŽlĂ©s comprennent l'augmentation de l'Ă©rosion cĂŽtiĂšre, l'augmentation du nombre et de la taille des incendies de forĂȘt et la rĂ©duction de l'accĂšs aux routes dâhiver aux collectivitĂ©s isolĂ©es du Nord. Des rĂ©ductions des Ă©missions nettes de GES sont nĂ©cessaires de toute urgence pour attĂ©nuer les nombreux effets de nouveaux changements climatiques. Les projets de dĂ©veloppement industriel et de travaux publics doivent dĂ©sormais Ă©valuer les effets des changements climatiques dans leur planification, leur conception et leur gestion. Les villes, les municipalitĂ©s et les communautĂ©s rurales doivent planifier soigneusement les nouveaux dĂ©veloppements rĂ©sidentiels pour Ă©viter les risques accrus d'inondation, d'Ă©rosion cĂŽtiĂšre ou d'incendie de forĂȘt. Les connaissances et l'expertise en sciences de la Terre font partie intĂ©grante de l'exploration et du dĂ©veloppement de nouveaux mĂ©taux et matĂ©riaux terrestres requis pour un avenir neutre en carbone, ainsi que dans la capture et la sĂ©questration du CO2 dans la Terre. Les sciences de la Terre sont Ă©galement au cĆur de l'adaptation de la sociĂ©tĂ© aux nouveaux rĂ©gimes climatiques et de la rĂ©duction des risques. Cela comprend l'anticipation, l'Ă©valuation et la gestion des Ă©vĂ©nements extrĂȘmes, l'Ă©laboration de nouvelles normes et directives pour les pratiques gĂ©otechniques et d'ingĂ©nierie, et la rĂ©vision des rĂ©glementations qui tient compte des changements climatiques. Les gĂ©oscientifiques ont Ă©galement un rĂŽle important dans l'Ă©ducation des Ă©tudiants et du public sur le fondement des mesures nĂ©cessaires. Le Canada occupe une position unique grĂące Ă son solide leadership gĂ©oscientifique mondial, sa vaste Ă©tendue et son territoire nordique pour tirer efficacement parti des activitĂ©s de recherche sur les changements climatiques. Les outils gĂ©oscientifiques et les compĂ©tences des gĂ©oscientifiques feront partie intĂ©grante de la prĂ©paration du Canada aux changements climatiques
Stratigraphy and sedimentology of early Pennsylvanian red beds at Lower Cove, Nova Scotia, Canada: the Little River Formation with redefinition of the Joggins Formation
The coastal cliffs along the eastern shore of Chignecto Bay, Nova Scotia contain one of the finest Carboniferous sections in the world. In 1843, Sir William Logan measured the entire section as the first project of the Geological Survey of Canada, and defined eight stratigraphic divisions. We have re-measured a section corresponding almost exactly with Loganâs Division 5 in bed-by-bed detail. The strata are exposed in the wave-cut platform and low-relief bluffs of a 2 km-long section at Lower Cove, near Joggins, north and south of Little River. This 635.8 metre-thick succession until now has been included within the basal part of the Joggins Formation, and overlies the Boss Point Formation. However, the studied strata are lithologically distinct, and are formally recognized as the new Little River Formation. This formation is bounded by regionally important surfaces and is traceable inland for 30 kilometres from its Lower Cove type section. Facies analysis indicates that it represents the deposits of a well-drained alluvial plain dissected by shallow rivers characterized by flashy flow. It can be clearly distinguished from the underlying Boss Point Formation (Loganâs Division 6) by its much smaller channels, and from the overlying Joggins Formation (Loganâs Division 4) by lack of coal seams and bivalve-bearing limestone beds. Palynological assemblages indicate that the Little River Formation is of probable late Namurian to basal Westphalian (basal Langsettian) age, and is a likely time-equivalent of the informal Grand-Anse formation of southeast New Brunswick.
Resumé
Les falaises cĂŽtiĂšres longeant le rivage oriental de la baie Chignectou, en Nouvelle-Ăcosse, abritent lâun des stratotypes carbonifĂšres les plus intĂ©ressants dans le monde. Sir William Logan avait mesurĂ© en 1843 lâensemble du stratotype dans le cadre du premier projet de la Commission gĂ©ologique du Canada et il avait dĂ©fini huit divisions stratigraphiques. Nous avons mesurĂ© Ă nouveau un stratotype correspondant presque exactement dans ses dĂ©tails couche par couche Ă la division 5 de Logan. Les strates affleurent dans une plate-forme dâĂ©rosion et des falaises de relief Ă©moussĂ© dâun secteur de deux kilomĂštres de longueur Ă lâanse Lower, prĂšs de Joggins, au nord et au sud de la riviĂšre Little. Cette succession de 635,8 mĂštres dâĂ©paisseur avait jusquâĂ maintenant Ă©tĂ© incluse Ă lâintĂ©rieur de la partie basale de la Formation de Joggins et elle recouvre la Formation de Boss Point. Les strates Ă©tudiĂ©es sont cependant lithologiquement distinctes et on les reconnaĂźt officiellement en tant que nouvelle Formation de Little River. Cette formation est limitĂ©e par des surfaces importantes Ă lâĂ©chelle rĂ©gionale; on peut la retracer Ă lâintĂ©rieur des terres sur 30 kilomĂštres Ă partir de son stratotype de lâanse Lower. Une analyse du faciĂšs rĂ©vĂšle quâil reprĂ©sente les dĂ©pĂŽts dâune plaine alluviale bien drainĂ©e, sectionnĂ©e par des riviĂšres peu profondes caractĂ©risĂ©es par des crues Ă©clair. On peut nettement la distinguer de la Formation sous-jacente de Boss Point (division 6 de Logan), grĂące Ă ses canaux beaucoup plus petits, ainsi que de la Formation sus-jacente de Joggins (division 4 de Logan), par lâabsence de couches houillĂšres et de couches de calcaire abritant des
lamellibranches. Les assemblages palynologiques rĂ©vĂšlent que la Formation de Little River remonte probablement Ă la pĂ©riode du Namurien tardif au Westphalien basal (Langsettien basal) et quâelle constitue vraisemblablement un Ă©quivalent chronologique de la Formation officieuse de Grande-Anse dans le sud-est du Nouveau-Brunswick
Sedimentology and stratigraphy of the type section of the Pennsylvanian Boss Point Formation, Joggins Fossil Cliffs, Nova Scotia, Canada
The 1125-m-thick type section of the Pennsylvanian Boss Point Formation is well exposed along the shore of the Bay of Fundy in Nova Scotia. We provide the first comprehensive account of the entirety of this formation, which comprises nearly one-third of the stratigraphic thickness of the Joggins Fossil Cliffs UNESCO World Heritage Site. The basal Chignecto Bay Member (0â91.5 m) is composed of redbeds, single-storey channel bodies with northerly paleoflow, and thin palustrine limestones. The middle Ward Point Member (91.5â951.7 m) contains up to 16 megacycles composed of alternations between thick packages of braided fluvial sandstone and fine-grained deposits. Although regional studies of the Boss Point Formation suggest that the fine-grained deposits are largely composed of lacustrine sediments, these intervals consist largely of poorly drained and well-drained floodplain deposits in the type section. The facies variations and southeast-directed paleoflow in the Ward Point Member record modest uplift associated with the growth of the salt-cored Minudie Anticline. The North Reef Member (951.7â1125 m) is composed of redbeds and two distinctive multistorey channel bodies. This uppermost member records a shift to more arid, oxidizing conditions, was the precursor to a major phase of salt withdrawal, and represents a transition to the overlying Little River Formation. The sedimentological framework, revised stratigraphy, and detailed measured section and map will provide a foundation for future study of this remarkable Pennsylvanian exposure
Individual differences in reward drive predict neural responses to images of food
A network of interconnected brain regions, including orbitofrontal, ventral striatal, amygdala, and midbrain areas, has been widely
implicated in a number of aspects of food reward. However, in humans, sensitivity to reward can vary significantly from one person to the
next. Individuals high in this trait experience more frequent and intense food cravings and are more likely to be overweight or develop
eating disorders associated with excessive food intake. Using functional magnetic resonance imaging, we report that individual variation
in trait reward sensitivity (as measured by the Behavioral Activation Scale) is highly correlated with activation to images of appetizing
foods (e.g., chocolate cake, pizza) in a frontoâstriatalâamygdalaâmidbrain network. Our findings demonstrate that there is considerable
personality-linked variability in the neural response to food cues in healthy participants and provide important insight into the neurobiological
factors underlying vulnerability to certain eating problems (e.g., hyperphagic obesity)
Near and Mid-IR Photometry of the Pleiades, and a New List of Substellar Candidate Members
We make use of new near and mid-IR photometry of the Pleiades cluster in
order to help identify proposed cluster members. We also use the new photometry
with previously published photometry to define the single-star main sequence
locus at the age of the Pleiades in a variety of color-magnitude planes.
The new near and mid-IR photometry extend effectively two magnitudes deeper
than the 2MASS All-Sky Point Source catalog, and hence allow us to select a new
set of candidate very low mass and sub-stellar mass members of the Pleiades in
the central square degree of the cluster. We identify 42 new candidate members
fainter than Ks =14 (corresponding to 0.1 Mo). These candidate members should
eventually allow a better estimate of the cluster mass function to be made down
to of order 0.04 solar masses.
We also use new IRAC data, in particular the images obtained at 8 um, in
order to comment briefly on interstellar dust in and near the Pleiades. We
confirm, as expected, that -- with one exception -- a sample of low mass stars
recently identified as having 24 um excesses due to debris disks do not have
significant excesses at IRAC wavelengths. However, evidence is also presented
that several of the Pleiades high mass stars are found to be impacting with
local condensations of the molecular cloud that is passing through the Pleiades
at the current epoch.Comment: Accepted to ApJS; data tables and embedded-figure version available
at http://spider.ipac.caltech.edu/staff/stauffer/pleiades07
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