The Quaternary History of Cumberland Sound, Southeastern Baffin Island: The Marine Evidence

Acoustic and core data from Cumberland Sound show that glacial ice derived from the Foxe Sector (Amadjuak Dome) of the Laurentide Ice Sheet advanced to the continental shelf at the mouth of the sound during a late phase of the Foxe Glaciation. The basal lithofacies/acoustic unit (Ai/BUD) in the sound is a massive, black diamicton. On the basis of strati-graphic, acoustic, lithologie and faunal evidence, this unit is interpreted as till. The till is overlain by an ice proximal to ice distal glacial-marine sediment sequence termed the Davis Strait Silt (DSS). The influence of ice retreat is reflected in the foraminiferal assemblages of the DSS. Rapid sedimentation rates in the sound prevailed during deposition of the DSS as shown by the conformable geometry of the DSS. Accelerator Mass Spectrometry dates on molluscs and foraminifera and a single conventional 14C date on disseminated organic material from ice proximal sediment of the DSS (lithofacies B and lower lithofacies C) indicate that the ice retreated rapidly from its probable maximum position on the shelf no earlier than ca. 13,400 BP and into the fiords along the coast of the sound by ca. 8900 BP. Deposition of ice-distal glacial marine sediments (lower lithofacies D) continued in the sound until ca. 7600 BP as the ice margin rapidly retreated into the fiords. Between ca. 8900 BP and ca. 8000 BP, the foraminiferal fauna show that the influence of glacial ice is remote and that "Atlantic Water" impinges on the seafloor. Postglacial sedimentation began in the sound at ca. 7600 BP. Retreat of the ice margin onto land made the fiord basins available as sediment catchments. The reduced sedimentation rates in the sound during this interval are indicated by the change to onlapping basin fill geometry of the Tiniktartuq Silt and Clay (TS&C). Calcareous foraminifera disappear from the sediments by ca. 6300 BP and are replaced by agglutinated foraminifera reflecting "Arctic Water" conditions at the seafloor. The TS&C is presently being deposited in the sound.Les données acoustiques ou issues des forages en provenance de la baie de Cumberland démontrent que la glace du secteur de Foxe (dôme d'Amadjuak) de l'Inlandsis laurentidien est parvenue sur le plateau continental, à l'embouchure de la baie, au cours d'une phase tardive de la Glaciation de Foxe. L'unité de base est un diamicton massif noir identifiée comme étant un till. Le till est recouvert par une séquence de sédiments glacio-marins proximaux et distaux appelée SiIt de Davis Strait. Le retrait glaciaire a eu des conséquences sur la nature des assemblages de foraminifères dans le SiIt de Davis Strait. Des taux rapides de sédimentation ont caractérisé le dépôt de ce silt comme le montre sa géométrie concordante. Les datations obtenues par accélérateur de particules sur les mollusques et les foraminifères et une datation au 14C conventionnelle sur du matériel organique disséminé dans le sédiment de contact glaciaire du SiIt montre que la glace s'est retirée rapidement à partir de sa position maximale probable sur le plateau continental, à partir d'environ 13 400 BP, pour s'écouler dans les fjords le long de la côte vers 8900 BP. Le dépôt des sédiments glacio-marins distaux s'est poursuivi dans la baie jusque vers 7600 BP, alors que la marge glaciaire se retirait rapidement vers les fjords. Entre 8900 BP et environ 8000 BP, l'influence des glaciers s'est peu fait sentir sur les foraminifères, et l'eau de l'Atlantique a envahi les fonds marins. La sédimentation postglaciaire a commencé dans la baie vers 7600 BP. Le changement de géométrie des Silts et argiles de Tiniktartuk devenus chevauchants reflète la diminution des taux de sédimentation dans le détroit au cours de cette période. Les foraminifères à test calcitique n'apparaissaient plus dans les sédiments vers 6300 BP et ont été remplacés par les foraminifères à test agglutiné, témoignant ainsi de la présence des eaux arctiques.Akustische und durch Bohrungen gewonnene Daten von der Cumberland-Bucht zeigen, daB glaziales Eis vom Foxe-Sektor (Amadjuak Dom) der laurentischen Eisdecke zur kontinentalen Plattform am Mund der Bucht wàhrend einer spàten Phase der Foxe-Vereisung vordrang. Die an der Basis befindliche Lithofazies/akustische Einheit (Ai/BUD) in der Bucht ist ein massives schwarzes Diamikton. Auf der Grundlage von stratigraphischen, akustischen, lithologischen und Fauna-Belegen wird dièse Einheit als Till interpretiert. Das Till wird von einer Sequenz glaziomariner Eis-proximal bis Eisdistal-Sedimente ûberlagert, welche Davis Strait Silt (DSS) genannt wird. Der EinfluB des Eisrùckzugs spiegelt sich in den Foraminiferen-Einhèiten des DSS. Schnelle Sedimentierungsraten herrschten in der Bucht wàhrend der Ablagerung des DSS vor, wie aus der gleich gelagerten Géométrie des DSS ersichtlich. Durch Teilchenbeschleuniger gewonnene Daten auf Mollusken und Foraminiferen und eine einzelne konventionelle 14C-Datierung auf verstreutem organischem Material von dem proximalen Eissediment des DSS (Lithofazies B und niedrigere Lithofazies C) zeigen, daB das Eis sich rasch von seiner wahrscheinlichen maximalen Position auf der Plattform nicht vor etwa 13,400 v.u.Z. zurùckzog und in die Fjorde entlang der Kûste der Bucht um efwa 8900 v.u.Z. ein-drang. Die Ablagerung der glazio-marinen distalen Sedimente (untere Lithofazies D) setzte sich in der Bucht weiter bis efwa 7600 v.u.Z. fort, als der Eisrand sich rasch in die Fjorde zurùckzog. Zwischen efwa 8900 v.u.Z. und efwa 8000 v.u.Z. zeigt die Fauna der Foraminiferen, dafî der EinfluB des glazialen Eises gering war, und daB "atlantisches Wasser" auf den Meeresgrund ùbergreift. Die postglaziale Sedimentierung begann in der Bucht um efwa 7600 v.u.Z. Die geringen Sedimentierungsraten in der Bucht wàhrend dieses Intervalls sind am Wechsel zu ùberlappender Géométrie der Beckenfùllung mit Tiniktartuq Schlamm und Lehm (TS&C) erkennbar

Accumulation in East Greenland Fjords and on the Continental Shelves Adjacent to the Denmark Strait over the Last Century Based on 210Pb Geochronology

Sediment (SAR) and mass (MAR) accumulation rates for the last 100 years are derived from 210Pb profiles of box cores collected in three fjords and on the continental shelf in the Kangerlussuaq region, East Greenland, and on the SW Iceland continental shelf. The MAR is lower on East Greenland (0.09 g/cm²·yr) than on SW Iceland (0.14 g/cm²·yr) because of differences in the biogenic component of the sediments, although SAR is similar. The differences in accumulation rates of the three East Greenland fjords are due to their dominant sediment sources and basin areas. Kangerlussuaq Fjord, the largest fjord, is dominated by iceberg sediment input and has a MAR of 0.43 g/cm²·yr at 50 km from the fjord head. Miki Fjord, the smallest fjord, is dominated by glaciofluvial sediment input with a MAR of 0.29 g/cm²·yr of sediment at 10 km from the fjord head. Nansen Fjord is intermediate in size, with an iceberg-dominated sediment supply; MAR is 1.01 g/cm²·yr near the fjord head and 0.17 g/cm²·yr at 20 km from the fjord head. 137Cs is used as a secondary indicator of sediment source, and the high activity level of 137Cs in Miki Fjord indicates glaciofluvial sediment sources. Zones of constant activity in some of the box cores are attributed to either bioturbation in the surface mixed layer or turbidites. We would be hesitant to extend the recent 210Pb-based accumulation rates to estimate the Holocene accumulation rates.On a calculé les taux d'accumulation de sédiments (TAS) et de masse (TAM) pour les cent dernières années à partir des profils du 210Pb dans des carottes rectangulaires prélevées dans trois fjords et sur le plateau continental de la région de Kangerlussuaq (est du Groenland), et sur le plateau continental du sud-ouest de l'Islande. Le TAM est plus faible dans l'est du Groenland (0,09 g/cm² par an) que dans le sud-ouest de l'Islande (0,14 g/cm² par an) en raison des différences dans la composante biogène des sédiments, bien que le TAS soit similaire. La différence entre les taux d'accumulation des trois fjords de l'est du Groenland est due à leurs sources majeures de sédiments et à leurs bassins de réception. Le fjord Kangerlussuaq, le plus grand des trois, est dominé par un apport de sédiments provenant d'icebergs et a un TAM de 0,43 g/cm² par an à 50 km de son extrémité amont. Le fjord Miki, qui est le plus petit, est dominé par un apport de sédiments fluvio-glaciaires avec un TAM de 0,29 g/cm² par an de sédiments à 10 km de son extrémité amont. Le fjord Nansen est de taille moyenne, et l'apport sédimentaire y provient en majorité d'icebergs; le TAM est de 1,01 g/cm² par an près de l'extrémité amont et de 0,17 g/cm² par an à 20 km de l'extrémité amont. Le 137Cs est utilisé comme indicateur secondaire de la source de sédiments, et le niveau d'activité élevé du 137Cs dans le fjord Miki révèle que les sédiments sont d'origine fluvio-glaciaire. Dans certaines des carottes rectangulaires, on attribue les zones d'activité constante soit à une bioturbation dans la couche mixte de surface, soit à des turbidités. Nous hésiterions à recourir aux récents taux d'accumulation fondés sur le 210Pb pour estimer les taux d'accumulation durant l'holocène

A robust, multisite Holocene history of drift ice off northern Iceland: implications for North Atlantic climate

An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative xray diffraction analysis of the \u3c 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between −0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6–7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz (HSQ) grains from VM129-191 west of Ireland casting doubt on the ice-transport origin. A pilot study on the provenance of Fe oxide grains in two cores that cover the last 1.3 and 6.1 cal. ka BP indicated a large fraction of the grains between 1 and 6 cal. ka BP were from either Icelandic or presently unsampled sources. However, there was a dramatic increase in Canadian and Russian sources from the Arctic Ocean ~1 cal. ka BP. These data may indicate the beginning of an Arctic Oscillation-like climate mode

A robust, multisite Holocene history of drift ice off northern Iceland: implications for North Atlantic climate

An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative xray diffraction analysis of the \u3c 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between −0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6–7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz (HSQ) grains from VM129-191 west of Ireland casting doubt on the ice-transport origin. A pilot study on the provenance of Fe oxide grains in two cores that cover the last 1.3 and 6.1 cal. ka BP indicated a large fraction of the grains between 1 and 6 cal. ka BP were from either Icelandic or presently unsampled sources. However, there was a dramatic increase in Canadian and Russian sources from the Arctic Ocean ~1 cal. ka BP. These data may indicate the beginning of an Arctic Oscillation-like climate mode

A Robust, Multisite Holocene History of Drift Ice off Northern Iceland: Implications for North Atlantic Climate

An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative xray diffraction analysis of the \u3c 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between −0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6–7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz (HSQ) grains from VM129-191 west of Ireland casting doubt on the ice-transport origin. A pilot study on the provenance of Fe oxide grains in two cores that cover the last 1.3 and 6.1 cal. ka BP indicated a large fraction of the grains between 1 and 6 cal. ka BP were from either Icelandic or presently unsampled sources. However, there was a dramatic increase in Canadian and Russian sources from the Arctic Ocean ~1 cal. ka BP. These data may indicate the beginning of an Arctic Oscillation-like climate mode

The Eastern Canadian Arctic at ca. 6 ka BP: A Time of Transition

The middle Holocene was a time of definite environmental transition in the Eastern Canadian Arctic. Based on several proxy indicators (pollen, diatoms, foraminifera, molluscs and nearshore sedimentation rates), it appears that a thermal maximum occurred around middle Holocene (6-4 ka), several thousand years after the insolation maximum — a lag caused by the thermal inertia of the earlier massive ice sheet. Terrestrial records indicate that a warming began around 6 ka, both in the subarctic (Labrador - Ungava) and on Baffin Island. Marine records, on the other hand, suggested major water structure changes around 6 ka both in the Northeastern Canadian Arctic and also along the East Greenland coast with evidence of a marine surface water temperature maximum at 8 ka. We hypothesize that the marine circulation changes, both along the Baffin Island and along the East Greenland coasts, were primarily driven by glacio-isostatic uplift of the Arctic Channels. With the cessation of water flow of Atlantic (warmer) origin, and decrease in water volume from the deeper parts of the Arctic Ocean through the Arctic Channels, the export through the Fram and Denmark straits increased and the water column changed. Changes in the concentration and duration of sea ice along the eastern Canadian coast would have had important repercussions on the biota of the coastal marine and terrestrial ecosystems.L'Holocène moyen a été une période de transition bien déterminée dans l'est de l'Arctique canadien. Selon de nombreux indicateurs (pollen, diatomées, foraminifères, mollusques et taux de sédimentation côtiers), il semble qu'un maximum thermique ait été atteint vers le milieu de l'Holocène (6-4 ka), plusieurs milliers d'années après le maximum d'insolation — un retard dû à l'inertie thermique causée par la présence de l'immense inlandsis. Les données terrestres démontrent qu'un réchauffement s'est amorcé vers 6 ka, à la fois dans le subarctique (Labrador, Ungava) et dans l'île de Baffin. Les données marines, d'autre part, indiquent qu'il y a eu des changements de structure de l'eau vers 6 ka à la fois dans le nord-est de l'Arctique canadien et le long de la côte du Groenland avec des indices de températures maximales marines de surface à 8 ka. Nous posons l'hypothèse selon laquelle les changements de circulation marine, à la fois le long de l'île de Baffin et le long de la côte est du Groenland ont été provoqués par le relèvement isostatique des chenaux arctiques. Avec l'arrêt de l'écoulement (plus chaud) en provenance de l'Atlantique et la diminution du cubage d'eau provenant des grandes profondeurs de l'océan Arctique dans les chenaux arctiques, l'évacuation par les détroits de Fram et du Danemark s'est accrue et la colonne d'eau s'est modifiée. Les changements de concentration et de durée de la glace marine le long de la côte est du Canada auraient eu d'importantes répercussions sur les écosystèmes marins côtiers et terrestres.Das mittlere Holozân war eine eindeutige Umwelt-Ùbergangszeit in der ostkanadischen Arktis. Gestùtzt auf zahlreiche Indikatoren (Pollen, Kieselalgen, Foraminiferen, Mollusken und die Sedimentationsrate am Ufer) scheint es, dap ein thermales Maximum um die Mitte des Holozàns erreicht wurde (6-4 ka), mehrere tausend Jahre nach dem Sonneneinstrahlungsmaximum - eine Verzôgerung, welche durch die thermale Trâgheit der frùheren massiven Eisdecke bewirkt wurde. Belege zu Land zeigen, daB eine Erwârmung um 6 ka begann, sowohl in der Subarktis (Labrador-Ungava) wie auch auf der Baffin-lnsel. Meeresbelege andererseits weisen auf bedeutende Wasserstruktur-Ànderungen um 6 ka, sowohl in der nordôstlichen kanadischen Arktis wie auch entlang der Kùste von Ost-Grônland, mit Anhaltspunkten fur maximale Wassertemperaturen an der Meeresober-flâche um 8 ka. Wir stellen die Hypothèse auf, daB die Wechsel der marinen Zirkulation, sowohl entlang der Baffin-lnsel wie auch der Kùsten von Ost-Grônland, in erster Linie durch die glazial-isostatische Anhebung der arktischen Kanâle hervorgerufen wurden. Mit der Beendigung des (wàrmeren) Wasserflusses vom Atlantik und der Abnahme des Wasservolumes von den tieferen Teilen des arktischen Ozeans durch die arktischen Kanâle nahm die Ausfuhr durch die Meeregen von Fram und Danemark zu, und die Wassersàule ânderte sich. Die Wechsel in der Konzentration und Dauer des Meereises entlang der ostkanadischen Kùste sollen bedeutende Auswirkungen auf Ôkosysteme an der Meereskùste und zu Land gehabt haben

American political affiliation, 2003–43: a cohort component projection

The recent rise and stability in American party identification has focused interest on the long-term dynamics of party bases. Liberal commentators cite immigration and youth as forces which will produce a natural Democratic advantage in the future while conservative writers highlight the importance of high Republican fertility in securing Republican growth. These concerns foreground the neglect of demography within political science. This paper addresses this omission by conducting the first ever cohort component projection of American partisan populations to 2043 based on survey and census data. A number of scenarios are modeled, but, on current trends, we predict that American partisanship will shift much less than the nation’s ethnic composition because the parties’ age structures are similar. Still, our projections find that the Democrats gain two to three percentage points from the Republicans by 2043, mainly through immigration, though Republican fertility may redress the balance in the very long term

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

Petermann Fjord is a deep (>1000 m) fjord that incises the coastline of north-west Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5 and 70 m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismo-acoustic facies in more than 3500 line kilometres of sub-bottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to bedrock or till surfaces (Facies I), subglacial deposition (Facies II), deposition from meltwater plumes and icebergs in quiescent glacimarine conditions (Facies III, IV), deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V) and the redeposition of material downslope (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann ice stream as 1080–1420 m3 a−1 per metre of ice stream width and an average deglacial erosion rate for the basin of 0.29–0.34 mm a−1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system, and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in rates over a glacial–deglacial transition. Our new glacial sediment fluxes and erosion rates show that the Petermann ice stream was approximately as efficient as the palaeo-Jakobshavn Isbræ at eroding, transporting and delivering sediment to its margin during early deglaciation

Prevalence and Correlates of Knowledge of Male Partner HIV Testing and Serostatus Among African-American Women Living in High Poverty, High HIV Prevalence Communities (HPTN 064)

Knowledge of sexual partners' HIV infection can reduce risky sexual behaviors. Yet, there are no published studies to-date examining prevalence and characteristics associated with knowledge among African-American women living in high poverty communities disproportionately affected by HIV. Using the HIV Prevention Trial Network's (HPTN) 064 Study data, multivariable logistic regression was used to examine individual, partner, and partnership-level determinants of women's knowledge (n=1,768 women). Results showed that women's demographic characteristics alone did not account for the variation in serostatus awareness. Rather, lower knowledge of partner serostatus was associated with having two or more sex partners (OR=0.49, 95%CI: 0.37-0.65), food insecurity (OR=0.68, 95%CI: 0.49-0.94), partner age>35 (OR=0.68, 95%CI: 0.49-0.94), and partner concurrency (OR=0.63, 95%CI: 0.49-0.83). Access to financial support (OR=1.42, 95%CI: 1.05-1.92) and coresidence (OR=1.43, 95%CI: 1.05-1.95) were associated with higher knowledge of partner serostatus. HIV prevention efforts addressing African-American women's vulnerabilities should employ integrated behavioral, economic, and empowerment approaches

From working collections to the World Germplasm Project: agricultural modernization and genetic conservation at the Rockefeller Foundation

This paper charts the history of the Rockefeller Foundation’s participation in the collection and long-term preservation of genetic diversity in crop plants from the 1940s through the 1970s. In the decades following the launch of its agricultural program in Mexico in 1943, the Rockefeller Foundation figured prominently in the creation of world collections of key economic crops. Through the efforts of its administrators and staff, the foundation subsequently parlayed this experience into a leadership role in international efforts to conserve so-called plant genetic resources. Previous accounts of the Rockefeller Foundation’s interventions in international agricultural development have focused on the outcomes prioritized by foundation staff and administrators as they launched assistance programs and especially their characterization of the peoples and ‘‘problems’’ they encountered abroad. This paper highlights instead how foundation administrators and staff responded to a newly emergent international agricultural concern—the loss of crop genetic diversity. Charting the foundation’s responses to this concern, which developed only after agricultural modernization had begun and was understood to be produced by the successes of the foundation’s own agricultural assistance programs, allows for greater interrogation of how the foundation understood and projected its central position in international agricultural research activities by the 1970s.Research for this article was supported in part by a grant-in-aid from the Rockefeller Archive Center