Clay minerals from sediment samples obtained on Astoria Fan
were analyzed by X-ray diffraction. Clay minerals are defined for
the purpose of this study as crystalline phyllosilicates less than two
microns in equivalent settling diameter. The clay minerals are subdivided
into the five common families: montmorillonite, chlorite,
vermiculite, illite, and kaolinite. One X-ray scan of a magnesium
ion saturated, ethylene glycol treated sample was sufficient for the
identification of all the clay minerals.
A typical Recent hemipelagic sediment contains about 40 percent
montmorillonite, 30 percent illite, and 30 percent chlorite. Neither
kaolinite nor vermiculite is detectable in these samples. These concentrations
are similar to those reported for Columbia River sediments.
The surface sediments have an identical clay mineral assemblage
from the head of Astoria Canyon to the outer edge of the fan
approximately 250 kilometers offshore. All of the Recent sediments
in piston cores from Astoria Fan are the same as the surface sediments
on the fan. This similarity indicates an unchanging source
during Recent time and a lack of any visible marine diagenesis after
burial.
X-ray traces of Pleistocene clay minerals are distinctly different
from those of the Recent. One can use this change in clay mineralogy
as a time marker across the fan. Presumably the Pleistocene
clays were formed under different weathering conditions caused
by different climatic conditions. / Graduation date: 1967
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28282 |
| Date | 02 May 1967 |
| Creators | Russell, Kenneth Lloyd |
| Contributors | Deffeyes, Kenneth S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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