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TitleHigh resolution dinoflagellate cyst record of environmental change in Effingham Inlet (BC, Canada) over the last millennium
AuthorBringué, M; Pospelova, V; Calvert, S E; Enkin, R J; Lacourse, T; Ivanochko, T
SourcePalaeogeography, Palaeoclimatology, Palaeoecology vol. 441, pt. 4, 2016 p. 787-810,
Alt SeriesEarth Sciences Sector, Contribution Series 20150065
Mediapaper; on-line; digital
File formatpdf
ProvinceWestern offshore region; British Columbia
AreaEffingham Inlet
Lat/Long WENS-125.2000 -125.1333 49.1000 49.0000
Subjectsmarine geology; paleontology; laminations; sediments; seismicity; Little Ice Age (LIA); Medieval Climate Anomaly; Operculodinium centrocarpum; Brigantedinium spp.; Dubridinium spp.; primary productivity reconstructions; dinoflagellate cyst assemblages; multivariate analyses
Illustrationslocation maps; stratigraphic columns; graphs; photographs; tables; photomicrographs; diagrams
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractWe present a high resolution sedimentary record of dinoflagellate cysts spanning the last ~900 years recovered from Effingham Inlet, a glacial fjord on the west coast of Vancouver Island, Canada. The combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters, together with restricted bottom water circulation in the silled fjord, fosters the preservation of laminated sediments in the inner basin of Effingham Inlet. Geochemical data are used to assess the sedimentary facies of the core, which is composed primarily of laminated units (50.2%) occasionally interrupted by 'seismites' (39.5%) and homogenous units (10.2%). The chronology of the ~2 m-long core is based on varve counting, fifteen 14C dates and is anchored by a seismite previously dated at AD 1946.
The dinoflagellate cyst assemblages are diverse (total of 47 taxa), abundant (average concentrations of 102,900 cyst g-1 of dry sediment), and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples. Overall, cyst assemblages are characterized by Operculodinium centrocarpum (36.2%) accompanied by Brigantedinium spp. (18.0%) and Dubridinium spp. (6.6%). Multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately, and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary.
Specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of climatic intervals known as the 'Medieval Climate Anomaly' (from the base of the record to ~AD 1230), the 'Little Ice Age' (~1230 to late 19th century) and the warming of the second half of the 20th century. The timing of these intervals are consistent with the regional paleoclimate and help constraining past climatic and oceanographic variability on the west coast of Vancouver Island. The origin of homogenous units in the sedimentary record of Effingham Inlet and paleoseismicity in the region are also discussed.
Summary(Plain Language Summary, not published)
Paleoclimate variations are identified using microfossils (dinoflagellate cysts) collected from sediments sampled from Effingham Inlet, an isolated fjord on the west coast of Vancouver Island. The sedimentary record also includes 4 event layers triggered by earthquakes, which are assigned improved dates going back 8 centuries.