Institution

the following peaks and weighting factors: 1) the area of
o
the 17 A peak of the glycolated sample is assigned to
montmorillonite, 2) four times the area of the
93
o
10 A peak of
the glycolated sample is assigned to illite, 3) twice the
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area of the 7 A peak in the untreated sample is assigned to
chlorite plus kaolinite, and 4) the contribution of chlorite
and kaolinite is determined as above. Some of the mixed-
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1 ayer materi al produces a 17 A peak upon glycol ati on and
is thus defined as montmorillonite. However, this method
does not detect any mixed-layer material that does not expand
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to 17 A.
All cl ay-mfneral di ffracti on patterns were recorded on
magnetic tape, processed in a computer program developed
by J.C. Hathaway, and peak intensities from the printout were
o
used to cal culate mi neral abundances. The area of the 17 A
glycolated peak (montmorillonite) was determined graphically
because of the inaccuracy of the computer baseline at low 28
angl es. Cal cul ati ons based on graphi c methods and those
based on intensities from the computer printout gave
virtually identical results for all other peaks.
Random-powder s i 1 t patterns were a 1 so recorded on
magnetic tape and processed by the same computer program.
Resul ts
Mineralogy determinations by Biscaye (1965) and
Hathaway (1972a) demonstrated that the northern portion of
the North Atlantic Basin and the northern continental margin
.)