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TitleInferred spring discharge characteristics of the Saguenay River, Quebec between ca. 1850 and ca. 1900 based on sediment texture proxy data
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AuthorSchafer, C T
SourceGeological Survey of Canada, Open File 8190, 2017, 52 pages, https://doi.org/10.4095/306170 (Open Access)
Image
Year2017
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
ProvinceQuebec
NTS22D/05; 22D/06; 22D/07; 22D/10; 22D/11; 22D/12
AreaSaguenay River; Saguenay Fiord; Lac Saint-Jean; Chicoutimi; Kenogami; St-Jean Vianney
Lat/Long WENS -71.8333 -70.7500 48.6333 48.3667
SubjectsNature and Environment; surficial geology/geomorphology; geochronology; engineering geology; surface waters; rivers; hydrologic environment; cores; piston cores; core analysis; climate; temperature; precipitation; alluvial deposits; deltaic sediments; silts; sands; varved deposits; textural analyses; grain size analyses; grain size distribution; history; depositional environment; sedimentary structures; radiometric dating; dams; storms; Atlantic Multi-Decadal Oscillation (AMO); North Atlantic Oscillation (NAO); El Nino; La Nina; hydrology; spring discharge; climate change; median diameter; gravity cores; proxy data; organic matter; lead-210; forest fires
Illustrationslocation maps; photographs; tables; bar graphs
ProgramDirector Office, GSC Atlantic Division
Released2017 11 08
AbstractThis study explores the potential of sediment textural variation as a proxy for spring freshet magnitude variation of the Saguenay River using fine sand to fine silt fractions that have been preserved in Saguenay River prodelta sediments deposited in the northwestern sector of the Saguenay Fiord's North Arm. High sedimentation rates and particulate organic matter fluxes have created a poorly oxygenated seafloor environment in parts of the North Arm that is virtually free of bioturbating organisms thereby facilitating the preservation of identifiable yearly increments of sediment that accumulate mostly during the River's annual spring freshet. A particle size (2.3 to 6.3 phi i.e., 0.220 mm to 0.013 mm) median diameter (MD) proxy of spring freshet magnitude determined at one cm intervals in a piston core collected in 1982 reflects year-to-year variability of the River's spring freshet magnitude during the 19th and most of the 20th century. This study focuses on the second half of the 19th century during which MD data records an estimated 19 year long interval of relatively small MD's (LMDI) that is estimated to have occurred between ~1871 and ~1888. Compared to the later decades of the 20th century MD record, the second half of the 19th century and the early part of the 20th century to about 1912 shows a relatively higher frequency of larger average MD that appears to imply a more frequent occurrence of stronger spring freshet intervals of comparatively lower temporal variability. Within the 1850 - 1912 interval, the MD proxy suggests a generally decreasing freshet magnitude trend from ~1865 to ~1871 that is followed by the LMDI period of reduced freshet magnitudes featuring MDs that are typically less than 55 um. The LMDI is succeeded by a generally increasing MD sequence suggestive of stronger freshets that persists until about 1912. An explanation for the apparent relatively low freshet magnitudes and low year-to-year variability of spring freshets during the LMDI in relation to previous and following decades is tentatively assigned to lesser amounts of snowfall during January and April and to relatively warmer January and February temperatures acting in concert with relatively lower March and April temperatures. These seasonal conditions show a general correspondence to warm (positive) Atlantic Multi-decadal Oscillation (AMO) phases that occurred between 1860 and 1891. In contrast, during the 20th century, cool (negative) AMO phases seem to be linked to intervals that include some of the highest recorded 20th century Saguenay River freshets witnessed in the 1970's. An analysis of the North Atlantic Oscillation (NAO)/MD relationship yielded mixed results. Not surprisingly, contradicting results also emerged in a comparison of AMO and NAO phases with respect to late 19th century local newspaper weather reports. In general, cooler spring and fall weather and stormy conditions were often associated with negative AMO conditions and with both positive and negative NAO's.
Summary(Plain Language Summary, not published)
The approximately 50 year-long proxy record(ca.1850-1900) of Saguenay River spring freshet magnitude reveals about a 19 year-long interval of apparently relatively reduced spring freshet magnitudes that occurred between the ~1871 and ~1888 sediment core horizons and that is referred to as the Low Median Diameter Interval (LMDI). Several decades immediately preceding the LMDI interval show a decreasing freshet magnitude trend. The LMDI is followed by an interval of apparently rising spring freshet magnitudes that persists until about 1912. Seasonal conditions during the LMDI show a general, albeit weak, correspondence to warm (positive) Atlantic Multidecadal (AMO) phases that occurred between 1860 and 1891.
GEOSCAN ID306170