Great Canadian Lagerstätten 1. Early Eocene Lagerstätten of the Okanagan Highlands (British Columbia and Washington State)

The Early Eocene Okanagan High lands series of lacustrine shale and coal deposits, in far western North Ameri ca, constitutes a significant group of fossil sites with exceptional preserva tion of a diverse suite of organisms (Lagerstätten). With contemporaneous basins arrayed across about 1000 kilo metres of southern British Columbia and northern Washington, these sites offer a unique opportunity to examine the paleoecology of terrestrial commu nities spanning a temperate, low-sea sonality landscape in a montane setting during a time of generally warm tem peratures across the globe. The Okana gan Highlands sites provide an unpar alleled comparative framework within which to examine this major turning point in terrestrial community develop ment during the emergence of their broad modern character.La série de dépôts lacustres de schiste et de charbon du début de l’Éocène des hautes terres d’Okanagan, aux con fins de l’ouest de l’Amérique du Nord, constituent un groupe important de sites fossiles particulièrement bien con servés de suites d’organismes diverses (Lagerstätten). De nos jours, ces sites forment en une bande d’environ 1 000 kilomètres, depuis le sud de la Colom bie-Britannique jusqu’au nord de l’État de Washington. Dans le contexte de réchauffement climatique, c’est l’occa sion ou jamais d’étudier la paléoécolo gie de communautés terrestres dans des conditions climatiques modérées dans un paysage de montagne à faible saisonnalité. Les sites des hautes terres d’Okanagan représentent un cadre de comparaison sans pareil permettant d’étudier les effets de ce tournant majeur sur le développement des prin cipales caractéristiques modernes de la communauté terrestre

Paleoenvironment of the Quilchena flora, British Columbia, during the Early Eocene Climatic Optimum

The Quilchena fossil locality is dated (51.5 ± 0.4 Ma) to the Early Eocene Climatic Optimum (EECO), and is reconstructed as the warmest and wettest of the Early Eocene upland sites from the Okanagan Highlands of British Columbia and northern Washington State. Mean annual temperature (MAT) is estimated from leaf margin analysis, using 55 dicot morphotypes, as 16.2°C ± 2.1°C / 14.6 ± 4.8°C. Using bioclimatic analysis of 45 nearest living relatives, a moist mesothermal climate is indicated (MAT 12.7-16.6°C; cold month mean temperature (CMMT) 3.5-7.9°C; mean annual precipitation (MAP) 103-157 cm/yr. Leaf size analysis estimates MAP at 121 ± 39 cm.a-1. Estimates from the climate leaf analysis multivariate program (CLAMP) corroborate these results, although with a slightly cooler MAT (13.3°C ± 2.1°C). Plants that support an interpretation of warm winters with minimal or no frost include Azolla, Glyptostrobus, Taxodium, Keteleeria, Pseudolarix, Eucommia, Dipteronia, Hovenia, and Ternstroemia and others. These thermophilous elements occur together with temperate genera such as Alnus, Betula, Ulmus, Calocedrus, and Fraxinus. Palynological assemblages at Quilchena are dominated by bisaccate conifers and Cupressaceae. Common angiosperms include Ulmus type, triporates, Pterocarya and Alnus. Insect fossils at Quilchena that today inhabit tropical and subtropical regions also support warm and equable climate without significant frost, and include obligate palm-feeding beetles (Pachymerina), which indicate CMMT perhaps as high as 8°C. These are found together with temperate aphids, wasps, giant lacewings, brown lacewings and a panorpoid scorpionfly, supporting an interpretation of equable climatic conditions during the EECO.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

(Table 1) AMS radiocarbon ages from ODP Hole 169-1034B

High-resolution pollen analysis of laminated marine sediments from ODP Hole 1034B in Saanich Inlet, British Columbia reveals changes in vegetation and inferred climate during the Holocene. Four main pollen zones are discerned using constrained cluster analysis. Although the timing of major vegetation changes at the Saanich Inlet is similar to other study sites in the Pacific Northwest, the composition of pollen assemblage zones is different from the mainland sites. Vegetation assemblages reconstructed from the pollen and spore record include a Douglas-fir (Pseudotsuga menziesii) parkland with abundant grass (Poaceae) and bracken (Pteridium) between 11,450 and 8300 BP (all ages are calibrated calendar years), oak (Quercus) savanna or parkland with high grass and bracken (8300-7040 BP), a mixed deciduous/coniferous forest with oak, western hemlock (Tsuga heterophylla) and Douglas-fir (7040-5750 BP), and the development of modern coastal temperate forest with the marked expansion of cedar (Cupressaceae), western hemlock, spruce (Picea) and Douglas-fir (5750-1050 BP). Climatic periods inferred from the cores include an early Holocene warm/dry interval (11,450-8300 BP), a warm period with mild winters (8300-7040 BP), a period of transitional mid-Holocene climate (7040-5750 BP), and the advent of a relatively cool/wet neoglacial climate after 5750 BP. Modern conifer forests and oak savannas became established by about 3800 BP. The Saanich Inlet pollen record indicates that vegetation and inferred climate change was particularly rapid between 8700 and 8300 BP when grass and bracken abruptly decrease and oak becomes a significant component of the paleovegetation. Because neoglacial conditions have prevailed from 3800 years to present in the Pacific Northwest, factors other than climate, such as anthropogenic modification of the landscape, may be responsible for the persistence of oak savannas

Holocene chironomid-inferred salinity and paleovegetation reconstruction from Kilpoola Lake, British Columbia

Salinity fluctuations in lakes of semi-arid regions have been recognised as indicators of paleoclimatic change and have provided a valuable line of evidence in paleoclimatic reconstruction. However, factors other than climate, including sedimentologic events, may also affect salinity. At Kilpoola Lake, early postglacial freshwater chironomids (Microtendipes, Sergentia, and Heterotrissocladius) occur in the basal sediments and yield a chironomid-inferred salinity of <0.03 g/l. Higher salinities, ranging from 1.0 to 3.5 g/l, with Cricotopus/Orthocladius and Tanypus (chironomids typical of saline environments) follow and, persist for most of the remainder of the Holocene. An inferred 450% salinity increase (from 1.6 to 7.3 g/l) occurred in the sediment above the Mount Mazama tephra, followed by a return to the pre-Mount Mazama salinity. The early Holocene pollen spectra are typical of open steppe, but the post-Mazama Artemisia pollen percentages are exceptionally high and are associated with silty clays. Pollen spectra following this Artemisia peak represent steppe communities and are consistent with regional trends. We suggest that the changes in chironomid communities and vegetation after deposition of the Mazama ash do not reflect a rapid shift to warmer or drier climate and evaporation, but rather an increased ionic concentration due to solutes derived from the freshly deposited tephra and perhaps in- washed silts and clays.Les fluctuations de la salinité dans les lacs des régions semi arides ont été considérées comme étant des indicateurs de changements paléoclimatiques et en ont facilité la reconstitution. Toutefois, certains facteurs autres que climatiques, y compris certains événements sédimentologiques, peuvent aussi modifier la salinité. Au Kilpoola Lake, les chironomides d'eau douce du début du postglaciaire (Microtendipes, Sergentia et Heterotrissocladius), trouvés dans les sédiments de la base, laissent présumer une salinité de <0,03 g/l. Des salinités plus élevées, de 1,0 à 3,5 g/l, avec Cricotopus/Orthocladius et Tanypus (chironomides caractéristiques des mileux salins) ont suivi et se sont maintenues presque tout le reste de l'Holocène. Les sédiments au-dessus du tephra du mont Mazama ont enregistré une augmentation de la salinité de 450 % (de 1,6 à 7,3 g/l), puis une diminution jusqu'à la salinité d'avant l'éruption du mont Mazama. Les spectres polliniques de l'Holocène inférieur sont caractéristiques de la steppe ouverte, mais les pourcentages d'Artemisia après l'éruption sont exceptionnellement élevés et sont associés aux argiles silteuses. Les spectres polliniques qui suivent le maximum d'Artemisia représen- tent les communautés de la steppe et concordent avec les tendances régionales. Les auteurs croient que les changements observés dans la communauté des chironomides et la végétation après le dépôt de la cendre de Mazama ne reflète pas un changement rapide vers un climat plus chaud et plus sec, mais plutôt une augmentation de la concentration ionique en raison de la présence de produits en solution issus de la couche de tephra nouvellement déposée.Die Salzgehalt-Fluktuationen in den Seen halbtrockener Gebiete sind als Indikatoren für paläoklimatische Veränderungen erkannt worden und haben wertvolles Beweismaterial bei der paläoklimatischen Rekonstruktion geliefert. Indessen könnten auch andere als klimatische Faktoren einschließlich sedimentologischer Ereignisse den Salzgehalt beeinflussen. Am Kilpoola-See treten frühe postglaziale Frischwasser-Chironomidae (Microtendipes, Sergentia und Heterotrissocladius) in den Basal-Sedimenten auf, und ergeben einen durch Chironomidae herbeigeführten Salzgehalt von <0.03 g/l. Höhere Salzgehalte, von 1.0 bis 3.5 g/ l mit Cricotopus/Orthocladius und Tanypus (für salzhaltige Umwelt typische Chironomidae) folgen und dauern während des größten Teils der übrigen Holozän-Zeit. In den Sedimenten über dem Tephra von Mount Mazama kam es zu einem Salzgehaltanstieg um 450 % (von 1.6 bis 7.3 g/l), worauf eine Senkung auf den Vor-Mount Mazama-Salzgehalt folgte. Die Pollen-Spektren aus dem frühen Holozän sind typisch für die offene Steppe, jedoch ist der Nach-Mazama Artemisia Pollen-Gehalt auberordentlich hoch und wird mit schlammigem Lehm in Verbindung gebracht. Die auf das Artemisia -Maximum folgenden Pollen-Spektren sind Steppen-Einheiten und stimmen mit den regionalen Tendenzen überein. Wir glauben, dass die Wechsel in den Chironomidae-Einheiten und in der Vegetation nach der Ablagerung der Mazama-Asche keinen schnellen Wechsel zu einem wärmeren oder trockeneren Klima und Verdunstung spiegeln, sondern vielmehr eine Zunahme der Ionen-Konzentration aufgrund von aufgelösten Elementen aus dem neu abgelagerten Tephra und vielleicht ausgewaschenem Schlamm und Lehm

Age determination of ODP sites 169-1033 and 169-1034

Two anomalous, gray, silty clay beds are present in ODP cores collected from Saanich Inlet, Vancouver Island, British Columbia, Canada. The beds, which date to about 10,500 14C yr BP (11,000 calendar years BP), contain Tertiary pollen derived from sedimentary rocks found only in the Fraser Lowland, on the mainland of British Columbia and Washington just east of the Strait of Georgia. Abundant illite-muscovite in the sediments supports a Fraser Lowland provenance. The clay beds are probably distal deposits of huge floods that swept through the Fraser Lowland at the end of the Pleistocene. Muddy overflow plumes from these floods crossed the Strait of Georgia and entered Saanich Inlet, where the sediment settled from suspension and blanketed diatom-rich mud on the fiord floor. The likely source of the floods is Late Pleistocene, ice-dammed lakes in the Fraser and Thompson valleys, which are known to have drained at about the time the floods occurred