Sediments of a portion of the central Oregon shelf between 17
and 339 m have been examined for modern foraminifera. Eighty-three
samples were collected from 33 stations along three traverses
located between 43° 16'N and 43° 50'N. One hundred fifty-five
benthic and nine planktonic species are recognized. Fifty-six benthic
species occur with a frequency of more than two percent in at
least one sample.
Benthic species are grouped into four distinct bathymetric
faunas. Elphidiella hannai and Buccella spp. are indicative of Fauna
A (17-50 m). Fauna B (50-100 m) is characterized by Buliminella
elegantissima and Elphidium magellanicum. In the rocky area off
Cape Arago Cassidulina californica, C. limbata, Cibicides fletcheri,
and C. lobatulus become dominant. Spiroplectammina biformis,
Textularia earlandi, and Trifarina angulosa are important species
of Fauna C (100-175 m). Abundant species of Fauna D (175-339 m)
include Eggerella advena, Epistominella exigua, and Uvigerina
juncea.
Species diversity increases offshore to a maximum of about 35
benthic species near 100 m and then decreases slightly with depth.
Standing crop is low nearshore, rises to a maximum of approximately
300 specimens per 20 cm³ between 125 and 150 m, and then
declines. Total benthic population reaches a maximum of approximately
6000 specimens per sample between 150 and 175 m. Values
then decrease to about 2000 specimens at 339 m. A maximum of
15 to 20 percent live benthic specimens occurs near 50 m. Planktonic
foraminifera constitute less than ten percent of the total population.
Maximum percentages generally occur shoaler than 100 m,
while maximum specimens per sample occur at the deepest stations.
Porcelaneous specimens do not exceed six percent of the benthic
population. Agglutinated foraminifera are more abundant than calcareous
specimens deeper than 100 m.
The frequency of occurrence of a species may vary by as much
as 25 percentage points from samples collected approximately 15 cm
apart. Statistical analysis of selected species indicates that sampling
density was not too close along any one traverse, although the traverses
possibly could have been spaced farther apart.
Miscellaneous biofacies trends indicate that: thecamoebians
are most abundant between 50 and 125 m; statoliths and otoliths
occur most frequently between 75 and 2OO m; highest ostracod
values are found between 25 and 150 m; and radiolarians generally
exceed foraminifera deeper than 250 m. / Graduation date: 1967
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28433 |
| Date | 08 May 1967 |
| Creators | Boettcher, Richard Scott |
| Contributors | Fowler, Gerald A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0028 seconds