Foraminifera as
Paleoceanographic Proxies of Canadian Fjords during the Last 1100 Years
Vázquez Riveiros, Natalia1, R.
Tim Patterson1 (1)
Foraminiferal and thecamoebian faunas
from the Seymour-Belize Inlet Complex (SBIC), a fjord network situated in the
mainland coast of British Columbia, were studied to asses climatic cycles and
trends impacting the area through the ~ AD 900 – 2002 interval.
Through cluster analysis, ordination
methods, and the use of foraminiferal-based transfer functions, a period of
weak estuarine circulation due to diminished precipitation, with feeble
incursions of ocean water into the basin, was recognized in the area during the
Medieval Warm Episode, which occurred here between ~ AD 900 and 1495. During
this time, bottom
waters in the SBIC became dysoxic to anoxic and only a low
diversity agglutinated foraminiferal fauna survived. Conversely, in the years
between AD 1574 and 1943, a very strong estuarine circulation developed, with
frequent renewals of the
bottom
waters by cold, oxygenated ocean currents
enhanced by a strong precipitation pattern. This period is concomitant with the
onset of the Little Ice Age in western
bottom
waters and the development of a diverse calcareous foraminiferal fauna.
This circulation pattern continued until 1943, when conditions similar to those
existing in the inlet prior to 1495 began to redevelop.
This study shows the potential of
high-resolution foraminiferal research in the development of accurate climate
chronologies. Foraminiferal-based transfer functions are established as very
functional, both as a validation of previously defined clusters and as a
quantitative instrument to estimate past values of environmental variables.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California