Early and Middle Wisconsinan Environments of Eastern Beringia: Stratigraphic and Paleoecological Implications of the Old Crow Tephra

The widespread Beringian Old Crow tephra occurs in Imuruk Lake (Alaska) core V, above the Blake paleomagnetic event and below Radiocarbon dates, which provide an extrapolated tephra age between 87 000 - 105 000 BP. Exposure KY-11 (Alaska), where the tephra occurs in a dated lacustrine sequence, provides corroboration. Fossil pollen records show that O.C.T. was deposited across northern Beringia on birch-shrub tundra vegetation during an interval of colder climate. A series of climatic oscillations followed tephra deposition. A prolonged period of cold-arid climate ( = marine isotope Stage 4) preceded an interval of warmer than present climate starting ca. 60 000 BP (beginning Stage 3). During this interval, designated the Koy-Yukon thermal event, an exposed Bering land bridge promoted an interglacial type climate that led to significant biotic changes and permafrost degradation. O.C.T. occurs on drift of the Mirror Creek Glaciation which is equivalent to other presumed Early Wisconsinan glaciations in Alaska and Yukon. These glaciations could not have occurred later than marine Stage 5. Stage 4 was fully as cold as Stage 2 (Late Wisconsinan), yet seems not to have been a time of extensive glaciation. The Middle Wisconsinan, 30 000 to more than 80 000 BP, was a nonglacial interval with several climate fluctuations, one of which, the Koy-Yukon thermal event, was warmer than at present.Le tephra de Old Crow, se manifeste, entre autres, au trou de forage V à Imuruk Lake, en Alaska. Puisqu'il se situe après l'inversion magnétique de Blake, mais au-delà de la portée des datations au radio-carbone, la date approximative de son dépôt doit se situer entre 87 000 et 105 000 BP. La coupe KY-11 (Alaska), où l'on trouve le tephra dans une séquence lacustre, appuie cette hypothèse. Les registres de pollen fossile démontrent que le tephra de Old Crow s'est déposé dans le nord de la Béringie dans un milieu de toundra arbustive à bouleau, au cours d'une période froide. Plusieurs oscillations climatiques se sont succédé par la suite. Une longue période de climat aride froid (phase isotopique océanique 4) a précédé un épisode au climat plus chaud que maintenant et qui a commencé vers 60 000 BP environ. Durant cet épisode (que l'on nomme ici Koy-Yukon), l'émergence du pont terrestre de Bering a contribué à l'avènement d'un climat de type interglaciaire, qui a provoqué des changements de type biotique importants et la dégradation du pergélisol. Le tephra de Old Crow surmonte des dépôts de la glaciation de Mirror Creek, qui correspond aux glaciations qui se sont produites en Alaska et au Yukon au cours du Wisconsinien inférieur. Ces glaciations n'ont pu avoir lieu après la phase isotopique 5. Pendant la phase 4, le climat était aussi froid que durant la phase 2 (Wisconsinien supérieur), mais il semble que cette période n'ait connu qu'un englacement limité. Il n'y a pas eu déglaciation pendant le Wisconsinien moyen (de 30 000 à plus de 80 000 BP), mais les fluctuations climatiques ont été nombreuses, dont l'épisode de Koy-Yukon.Das weitverbreitete Tephra von Old Crow, Beringia, findet man auch am Bohrioch V von Imuruk Lake (Alaska). Da es nach der Inversion von Blake und vor Radiokarbondatierungen liegt, mufi die annâhernde Zeit der Tephra-Ablagerung zwischen 87 000 -105 000 v.u.Z. Iiegen. Der Schnitt KY-11 (Alaska), wo das Tephra in einer datierten Seesediment-Folge vorkommt, bestâtigt diese Datierung. Belege von fossilem Pollen zeigen, daf3 Old Crow Tephra in Nord-Beringia in einem Milieu von Birken-Busch-Tundra wâhrend einer Période kàlteren Klimas abgelagert wurde. Auf die Tephra-Ablagerung folgte eine Série von Klima-Schwankungen. Eine lângere Période von kalttrockenem KIima ( = marine isotopische Phase 4) ging einer Phase, die warmer als das heutige Klima war und die etwa 60 000 v.u.Z. begann (Beginn der Phase 3) voraus. Wâhrend dieser Zeitphase. die das thermische Koy-Yukon genannt wird, bewirkte eine ausgesetzte Bering Land-Brucke ein Klima des interglazialen Typus, welches zu bedeutenden biotischen Verànderungen und Permafrost Abtragungen fuhrte. Old Crow Tephra findet sich uber den Ablagerungen der Mirror Creek Vereisung, welche anderen mutmaGlich frùhen Wisconsin Vereisungen in Alaska und Yukon entspricht. Diese Vereisungen kônnen nicht spâter als in der marinen Phase 5 stattgefunden haben. Die Phase 4 war so kalt wie die Phase 2 (spates Wisconsin), scheint jedoch keine Zeit extensiver Vereisung gewesen zu sein. Das mittlere Wisconsin, von 30 000 bis mehr als 80 000 v.u.Z., war eine nicht glaziale Zeitspanne mit gewissen Klima-Schwankungen, deren eine, das thermische Koy-Yukon. warmer als die Jetztzeit war

The Last (Koy-Yukon) Interglaciation in the Northern Yukon: Evidence from Unit 4 at Ch’ijee’s Bluff, Bluefish Basin

The effects of predicted anthropogenic warming can be assessed in part by documenting responses to past warming events. One of the most pronounced warmings was the last interglaciation - stage 5 of the marine isotope record. A large multinational and multidisciplinary project (CELIA) was launched recently in order to gain detailed knowledge of the climate during stage 5. Several key exposures were identified by CELIA; one of them is Ch'ijee's Bluff on the Porcupine River, northern Yukon. Pollen, plant and insect macrofossils and stratigraphie evidence from Ch'ijee's Bluff show that the part of Ch'ijee's Unit 4 that is above and younger than Old Crow tephra (OCt) was deposited during an interval of climate warmer than present. When OCt was dated at 85 ka BP, the subsequent warming interval was presumed to be correlative with the early part of marine isotope stage 3. New dates on OCt show it to be 140-150 ka BP, and this means that the warm interval discussed here is more likely of stage 5 than stage 3 age. We apply the informal epithet, "Koy-Yukon interglaciation", to it and compare the Ch'ijee's Bluff Unit 4 sequence with other east Beringian sites that contain both Old Crow tephra and putative interglacial deposits.Les conséquences du réchauffement anthropique attendu pourraient en partie être évaluées à partir de nos connaissances sur les réchauffements climatiques antérieurs. Le réchauffement climatique le plus important s'est produit au cours du dernier interglaciaire (stade isotopique 5). Dans le but d'acquérir une meilleure connaissance du climat durant le stade 5, on a créé un important projet multidisciplinaire et multinational (CELIA). On a identifié plusieurs coupes clés dont celle de Ch'ijee's Bluff, de la Porcupine River, dans le nord du Yukon. Les indices fournis par le pollen, les végétaux, les macrofossiles d'insectes et la stratigraphie de Ch'ijee's Bluff démontrent que la partie de l'unité n 4 plus jeune que le tephra de Old Crow et située au-dessus a été déposée durant un intervalle plus chaud qu'aujourd'hui. Quand on a daté à 85 ka BP le tephra de Old Crow, on présumait que l'intervalle de réchauffement subséquent était corrélatif au stade isotopique 3, Les nouvelles dates le font maintenant remonter à 140-150 ka BP, ce qui signifie que le réchauffement climatique appartient plutôt au stade 5. On lui a attribué le nom informel de « interglaciaire de Koy-Yukon ». On a comparé la séquence de l'unité n 4 avec celle d'autres sites de Béringie qui renferment à la fois le tephra de Old Crow et des dépôts considérés comme étant interglaciaires.Die Auswirkungen einer erwarteten anthropogenen Erwàrmung kann man teilweise abschâtzen, indem man die Ergebnisse vergangener klimatischer Erwârmungen dokumentiert. Eine der herausragendsten klimatischen Erwârmungen war die letzte Interglazialzeit - Stadium 5 des marinen Isotop-Belegs. Kùrzlich hat man ein breitangelegtes multinationales und multidisziplinàres Projekt (CELIA) gestartet, um detaillierte Kenntnis ùber das Klima wàhrend des Stadium 5 zu erhalten. CELIA hat mehrere Schlussel-Schnitte identifiziert; einer davon ist Ch'ijee's Bluff am Porcupine River, nôrdliches Yukon. Die von Pollen, Pflanzen, Insektenmakrofossilen und Stratigraphie von Ch'ijee's Bluff gelieferten Anhaltspunkte zeigen, dass der Teil der Ch'ijee's-Einheit 4, der ùber Old Crow Tephra (OCt) liegt und jùnger ist, wâhrend eines klimatischen Intervalls. das warmer war als gengewârtig, abgelagert wurde. AIs man OCt auf 85 ka v. u. Z. datierte. nahm man an. dass das folgende Erwàrmungs-lntervall mit dem frùhen Teil des marinen Isotop-Stadiums 3 korrelierte. Neue Daten auf OCt zeigen, dass dieses 140-150 ka v. u. Z. ait ist, und das bedeutet, dass das warme Intervall, von dem hier die Rede ist. wohl eher dem Stadium 5 als dem Stadium 3 zugehôrt. Wir benutzen die informelle Bezeichnung "Koy-Yukon Interglazialzeit" und vergleichen die Ch'ijee's Bluff 4-Sequenz mit anderen Plâtzen von Ost-Bering, die sowohl Old Crow Tephra enthalten wie auch Ablagerungen, die man fur interglaziale Ablagerungen hait

Plant and Insect Fossils from the Mayo Indian Village Section (Central Yukon): New Data on Middle Wisconsinan Environments and Glaciation

The Mayo Indian Village Section in central Yukon contains the Mayo Till, representing the Wisconsinan McConnell Glaciation, underlain by fluvial sediments with rare detrital organics. Previous 14C dates from the till or underlying sediments have failed to adequately define the age of the McConnell Glaciation. A new accelerator date (29.6 ka BP) on seeds of Corispermum hyssopifolium from subtill deposits shows that the McConnell Glaciation is probably Late Wisconsinan in age and that it correlates with the Kluane Glaciation (Kluane Lake area), McCauley Glaciation (Snag-Klutlan region) and the glaciation represented by « Till D » at the Tom Creek Section (Liard Plain). This conclusion and a new date on Old Crow tephra mean that the Reid, Mirror Creek and possibly Shakwak glaciations are of lllinoian age. Plant fossils (pollen and seeds) and insect fossils from detrital organics associated with the 29.6 ka BP date portray an essentially treeless environment. Even though typical low arctic plants such as heaths, shrub birch and alder are rare to absent, both pollen and macro-fossils suggest a climate no colder than present low arctic tundra, although, it was probably drier. Spruce may have survived in the region, but only as small groves rather than as a riparian forest.La coupe du village indien de Mayo renferme le Till de Mayo, témoin de la Glaciation de McConnell datant du Wisconsinien, sous lequel se trouvent des sédiments fluviatiles comprenant des matériaux organodétritiques rares. Les datations au 14C du till et des sédiments sous-jacents obtenues antérieurement n'avaient pas permis de dater avec précision l'âge de la Glaciation de McConnell. La nouvelle date de 29,6 ka obtenue par accélérateur sur des graines de Corispermum hyssopifolium provenant des dépôts sous-jacents au till indique que la Glaciation de McConnell date probablement du Wisconsinien supérieur et qu'elle correspond aux glaciations de Kluane (Kluane Lake) et de McCauley (région de Snag-Klutan) et à la glaciation représentée par le "Till D" dans la coupe de Tom Creek (Liard Plain). À partir de cette conclusion et grâce à une nouvelle datation sur le tephra de Old Crow, on peut croire que les glaciations de Reid, de Mirror Creek et probablement de Shakwak sont d'âge illinoien. Les fossiles de végétaux (pollen et graines) et d'insectes trouvés dans les sédiments organodétritiques associés à la date de 29.6 ka BP témoignent d'un milieu en grande partie dépourvu d'arbres. Même si les végétaux caractéristiques du bas Arctique comme les Éricacées, l'aulne et le bouleau arbustif sont rares ou absents, le pollen et les macrofossiles laissent entrevoir un climat qui n'était pas plus froid que le climat actuel de la toundra du bas Arctique, mais probablement plus sec. Les épinettes ont peut-être survécu dans la région mais seulement sous forme de bosquets et non de forêt riparienne.Das Profil aus dem indianischen Dorf Mayo, Zentral-Yukon, enthàlt das Till von Mayo, das die McConnell-Vereisung im Wiskonsinium bezeugt und unter dem sich Flusssedimente mit seltenem organischem Erosionsmaterial befinden. Frùhere 14C-Daten von dem Till oder darunter liegenden Sedimenten fùhrten nicht zu einer adâquaten Bestimmung des Alters der McConnell-Vereisung. Ein neues, mit Hilfe eines Beschleunigers auf Samen von Corispermum hyssopifolium in den Ablagerungen unter dem Till gefundenes Datum (29.6 ka v.u.Z.) zeigt, dass die McConnell-Vereisung môglicherweise im spàten Wiskonsinium stattfand und mit den Vereisungen von Kluane (Kluane-See-Gebiet), McCauley (Snag-Klutlan-Gebiet) und dem durch das "Till D" reprasentierten Profil von Tom Creek (Liard Plain) korreliert. Dièse Folgerung und ein neues Datum auf dem Tephra von Old Crow bedeuten, dass die Vereisungen von Reid, Mirror Creek und môglicherweise Shakwak dem lllinoium zugeordnet werden kônnen. Pflanzenfossile (Pollen und Samen) und Insektenfossile aus organischem Erosionsmaterial, das mit dem 29.6 ka v.u.Z. Datum in Verbindung gebracht wird. zeichnen eine im wesentlichen baumlose Umwelt. Auch wenn typische Pflanzen der unteren Arktis wie Heidekraut, Buschbirke und Erie selten bis nicht vorhanden sind. belegen sowohl Pollen wie Makrofossile ein Klima, das nicht kâlter war als das gegenwàrtig in der Tundra der unteren Arktis herrschende, wenn auch môglicherweise trockener. Fichten haben wohl in dem Gebiet uberlebt aber nur in kleinen Wàldchen und nicht als Uferwald

Circum-Arctic Late Tertiary/Early Pleistocene Stratigraphy And Environments - A Preface

...During the 1980s the Geological Survey of Canada (GSC) and the U.S. Geological Survey (USGS) initiated a program of joint workshops and cooperative field excursions. The first meeting took place in Calgary, Alberta, in 1984. It dealt with correlation of Quaternary deposits in northwestern North America, but touched on the Tertiary. A second GSC/USGS workshop in early 1987 concerned the Quaternary history of interior basins of Alaska and Canada, but once again the Tertiary became an item of discussion because some of the basins contain a thick sequence of Pliocene and Miocene sediments. It was apparent from the questions that arose at these meetings that there was a need for a dedicated forum on the late Tertiary. The authors organized and convened a workshop with that theme in Denver, Colorado, in October 1987. The papers in this special issue are based on presentations and discussions at that meeting. ..

The Aassociation Between Rest-Activity Rhythms and Glycemic Markers: the Us National Health and Nutrition Examination Survey, 2011-2014

OBJECTIVES: Previous studies conducted in mostly homogeneous sociodemographic samples have reported a relationship between weakened and/or disrupted rest-activity patterns and metabolic dysfunction. This study aims to examine rest-activity rhythm characteristics in relation to glycemic markers in a large nationally representative and diverse sample of American adults. METHODS: This study used data from the National Health and Nutrition Examination Survey 2011-2014. Rest-activity characteristics were derived from extended cosine models using 24-hour actigraphy. We used multinomial logistic regression and multiple linear regression models to assess the associations with multiple glycemic markers (i.e., glycated hemoglobin, fasting glucose and insulin, homeostatic model assessment of insulin resistance, and results from the oral glucose tolerance test), and compared the results across different categories of age, gender, race/ethnicity, and body mass index. RESULTS: We found that compared to those in the highest quintile of F statistic, a model-fitness measure with higher values indicating a stronger cosine-like pattern of daily activity, participants in the lowest quintile (i.e, those with the weakest rhythmicity) were 2.37 times more likely to be diabetic (OR Q1 vs. Q5 2.37 (95% CI 1.72, 3.26), p-trend \u3c .0001). Similar patterns were observed for other rest-activity characteristics, including lower amplitude (2.44 (1.60, 3.72)), mesor (1.39 (1.01, 1.91)), and amplitude:mesor ratio (2.09 (1.46, 2.99)), and delayed acrophase (1.46 (1.07, 2.00)). Results were consistent for multiple glycemic biomarkers, and across different sociodemographic and BMI groups. CONCLUSIONS: Our findings support an association between weakened and/or disrupted rest-activity rhythms and impaired glycemic control among a diverse US population

Acute Alcohol and Cognition: Remembering What It Causes Us to Forget

Addiction has been conceptualized as a specific form of memory that appropriates typically adaptive neural mechanisms of learning to produce the progressive spiral of drug-seeking and drug-taking behavior, perpetuating the path to addiction through aberrant processes of drug-related learning and memory. From that perspective, to understand the development of alcohol use disorders it is critical to identify how a single exposure to alcohol enters into or alters the processes of learning and memory, so that involvement of and changes in neuroplasticity processes responsible for learning and memory can be identified early on. This review characterizes the effects produced by acute alcohol intoxication as a function of brain region and memory neurocircuitry. In general, exposure to ethanol doses that produce intoxicating effects causes consistent impairments in learning and memory processes mediated by specific brain circuitry, whereas lower doses either have no effect or produce a facilitation of memory under certain task conditions. Therefore, acute ethanol does not produce a global impairment of learning and memory, and can actually facilitate particular types of memory, perhaps particular types of memory that facilitate the development of excessive alcohol use. In addition, the effects on cognition are dependent on brain region, task demands, dose received, pharmacokinetics, and tolerance. Additionally, we explore the underlying alterations in neurophysiology produced by acute alcohol exposure that help to explain these changes in cognition and highlight future directions for research. Through understanding the impact acute alcohol intoxication has on cognition, the preliminary changes potentially causing a problematic addiction memory can better be identified

Overview of optical BCI research at NUI Maynooth

A brain-computer interface (BCI) is a device that provides a user with an alternative means of interactive communication, rather than the usual modes via physical gestures/speech. Thus it acts as a neural prosthesis bypassing the normal output pathways of the brain, i.e. spinal cord and periphery cascade. An optical BCI uses optical means of determining the user's mental intent, e.g. to turn on a light switch, by spectroscopic analysis of the intact brain

Overview of optical BCI research at NUI Maynooth

A brain-computer interface (BCI) is a device that provides a user with an alternative means of interactive communication, rather than the usual modes via physical gestures/speech. Thus it acts as a neural prosthesis bypassing the normal output pathways of the brain, i.e. spinal cord and periphery cascade. An optical BCI uses optical means of determining the user's mental intent, e.g. to turn on a light switch, by spectroscopic analysis of the intact brain

Triple wavelength LED driver for optical brain–computer interfaces

A dedicated triple wavelength LED driver is presented for optical brain–computer interfacing (BCI). The solution caters for the constraints of a common-anode grounded case and modulation up to several kilohertz that allows source separation of light that has backscattered from the brain. With total harmonic distortion of 0.95% and a frequency range of ~40 kHz, the driver has application in a continuous wave optical BCI. Other modulation strategies such as time division multiplexing (TDM) are catered for, owing to input DC coupling. Linearity in the optical output is maintained by the ‘load sensing’ differential op-amp on the LED’s current limiting resistor, which is the basis for the V-I conversion

A Concept for Extending the Applicability of Constraint-Induced Movement Therapy through Motor Cortex Activity Feedback Using a Neural Prosthesis

This paper describes a concept for the extension of constraint-induced movement therapy (CIMT) through the use of feedback of primary motor cortex activity. CIMT requires residual movement to act as a source of feedback to the patient, thus preventing its application to those with no perceptible movement. It is proposed in this paper that it is possible to provide feedback of the motor cortex effort to the patient by measurement with near infrared spectroscopy (NIRS). Significant changes in such effort may be used to drive rehabilitative robotic actuators, for example. This may provide a possible avenue for extending CIMT to patients hitherto excluded as a result of severity of condition. In support of such a paradigm, this paper details the current status of CIMT and related attempts to extend rehabilitation therapy through the application of technology. An introduction to the relevant haemodynamics is given including a description of the basic technology behind a suitable NIRS system. An illustration of the proposed therapy is described using a simple NIRS system driving a robotic arm during simple upper-limb unilateral isometric contraction exercises with healthy subjects