Transcript FORAM COILING DIRECTIONS GEOL 3213

FORAM COILING
DIRECTIONS
GEOL 3213
Globorotalia truncatulinoides
• Bolli (1950, 1951) discovered that
the evolution of coiling directions of
certain species of planktic forams
varied and tended to be dominantly
dextral or sinistral at some times.
• He suggested that this might have
stratigraphic value.
• Ericson, Wollin, & Wollin (1954)
successfully tested this hypothesis.
Their figures are reproduced herein.
Coiling Distribution Map – Recent North Atlantic
• From Ericson et
al. (1954)
• Note the
dominantly
right- & leftcoiled regions.
• What is the
percentage &
direction near
Bermuda?
Coiling Direction Distributions in Cores
• Two piston cores 28 km
apart 360 km SW of the
Canary Islands
• Note the extremely similar
curves.
• Can they be correlated?
• Which cored area had the
faster rate of deposition?
Coiling Direction Distributions in Cores
• 4 piston cores along the Atlantic equator along a traverse 475 km
long.
• How would you correlate these sections?
• Which cored region had the fastest rate of deposition?
• Which cored region had the slowest rate of deposition?
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