foram coiling directions geol 3213. globorotalia truncatulinoides bolli (1950, 1951) discovered that...

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- & left-coiled 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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