Distribution of Recent deep-sea benthonic foraminifera ...
(Eds.), Proceedings of the First International Conference on Plank- Styzen, M. J . 1980. Late Eocene foraminiferal systematics, biostratonic Microfossils (Vol. 2). Geneva: E. J. Brill, Leiden. tigraphy and paleoecology of DSDP hole 267B, southeast Indian Ocean. Unpublished master's thesis, Northern Illinois Schianger, S.O., Douglas, R.G., Lancelot, Y., Moore, T. C., and Roth, University. P. H. 1973. Fossil preservation and diagenesis of pelagic carbonates from the Magellan Rise, central north Pacific Ocean. In E. L. Weissel, J . K., and Hayes, D. E. 1972. Magnetic anomalies in the Winterer et al. (Eds.), Initial reports of the Deep Sea Drilling Project, southeast Indian Ocean. In Antarctic Research Series (Vol. 19). Vol. 17. Washington, D.C.: U.S. Government Printing Office. Washington, D.C.: American Geophysical Union.
Distribution of Recent deep-sea benthonic foraminifera from the southwest Indian Ocean BRUCE H. CORLISS
Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543
Deep-sea benthonic foraminifera have been studied from a suite of 58 trigger core tops in the Crozet, Madagascar, and Mascarene Basins of the southwest Indian Ocean from 9° to
45°S latitude and 45° to 80°E longitude (figure 1) to determine faunal/water-mass relationships. Principal component analysis of the faunal data reveals distinct faunal trends related to depth and bottom-water potential temperature (figure 1). Principal component 1 represents an average of all of the fauna! data. The negative values of principal component 2 reflect the importance of Epistominella umbonifera and are found generally south of 35°S latitude in the Crozet Basin and on the flanks of the Madagascar, Southwest Indian, and Southeast Indian Ridges. These values are associated with bottom-water potential temperatures ranging from — 0.1° to 1.2°C, with the high relative values ( — 0.4) found generally with potential temperatures of :5 0.8°C. Positive values of principal
40' 50' 60' 70' 80'E
Figure 1. Distribution of principal component 2 of the benthonic foraminiferal data from the southwest Indian Ocean plotted with water depth and potential temperature. The range of values is from — ito + 1; negative values of principal component 2 reflect the Importance of Epistominella umbonifsic, and positive values reflect the importance of Planuilna wu.Ilerstorfi; rare species (< 3 percent), Globocassidullna subglobosa, and Astrononion echolsL
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component 2 reflect the importance of Planulina wueller-
storfi, rare species (:5 3 percent), Globocassidulina subglobosa, and Astrononion echolsi and are found on the Central Indian and Madagascar Ridges with bottom-water potential temperatures of 0.4° to 1.2°C, with high relative values (2: 0.4) found with potential temperatures of 1.2°C. The third principal component (figure 2) divides this last group into two subgroups. High negative values of principal component 3 reflect the importance of Globocassidulina subglobosa, and high positive values reflect the importance of Epistominella exiqua, Planulina wuellerstorfi, and Pullenia bulloides. To understand better the faunal distribution, the data from the 58 samples have been divided into three groups and used to construct latitudinal transects across the Crozet Basin, Madagascar Basin, and the Amirante Passage. Piston cores presently are being studied in the Madagascar transit. These studies will be used to contruct profiles of the benthonic foraminiferal faunas back through time, and the profiles will be compared with the present faunal distribution. The change in the faunal distribution will then be used to infer changes in the water mass distributions during the Quaternary. This research was supported by National Science Foundation grant DPP 78-21105. G. P. Lohmann is gratefully acknowledged for assistance with the principal component analysis.
1980 REVIEW
.
PR/NC/PAL COMPONENT 2 -08
-08 -04 00 04 08
-04
00
04
0.8
Figure 2. Principal component 2 versus principal component 3. Positive values of principal component 2 indicate the importance of Planulina wuellerstorfi, rare species (s 3 percent), Globocassiduilna subglobo.a, and Astrononion echolsL Negative values indicate the importance of Epistominella umbonifera. Positive values of principal component 3 indicate the importance of Epistominella exiqua6 P. wuellerstorfl, and Puelienla buioidss. Negative values indicate the dominance of G.. subglobosa.
133
Distribution of Recent deep-sea benthonic foraminifera from the southwest Indian Ocean BRUCE H. CORLISS
Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543
Deep-sea benthonic foraminifera have been studied from a suite of 58 trigger core tops in the Crozet, Madagascar, and Mascarene Basins of the southwest Indian Ocean from 9° to
45°S latitude and 45° to 80°E longitude (figure 1) to determine faunal/water-mass relationships. Principal component analysis of the faunal data reveals distinct faunal trends related to depth and bottom-water potential temperature (figure 1). Principal component 1 represents an average of all of the fauna! data. The negative values of principal component 2 reflect the importance of Epistominella umbonifera and are found generally south of 35°S latitude in the Crozet Basin and on the flanks of the Madagascar, Southwest Indian, and Southeast Indian Ridges. These values are associated with bottom-water potential temperatures ranging from — 0.1° to 1.2°C, with the high relative values ( — 0.4) found generally with potential temperatures of :5 0.8°C. Positive values of principal
40' 50' 60' 70' 80'E
Figure 1. Distribution of principal component 2 of the benthonic foraminiferal data from the southwest Indian Ocean plotted with water depth and potential temperature. The range of values is from — ito + 1; negative values of principal component 2 reflect the Importance of Epistominella umbonifsic, and positive values reflect the importance of Planuilna wu.Ilerstorfi; rare species (< 3 percent), Globocassidullna subglobosa, and Astrononion echolsL
132
ANTARCTIC JOURNAL
-.
component 2 reflect the importance of Planulina wueller-
storfi, rare species (:5 3 percent), Globocassidulina subglobosa, and Astrononion echolsi and are found on the Central Indian and Madagascar Ridges with bottom-water potential temperatures of 0.4° to 1.2°C, with high relative values (2: 0.4) found with potential temperatures of 1.2°C. The third principal component (figure 2) divides this last group into two subgroups. High negative values of principal component 3 reflect the importance of Globocassidulina subglobosa, and high positive values reflect the importance of Epistominella exiqua, Planulina wuellerstorfi, and Pullenia bulloides. To understand better the faunal distribution, the data from the 58 samples have been divided into three groups and used to construct latitudinal transects across the Crozet Basin, Madagascar Basin, and the Amirante Passage. Piston cores presently are being studied in the Madagascar transit. These studies will be used to contruct profiles of the benthonic foraminiferal faunas back through time, and the profiles will be compared with the present faunal distribution. The change in the faunal distribution will then be used to infer changes in the water mass distributions during the Quaternary. This research was supported by National Science Foundation grant DPP 78-21105. G. P. Lohmann is gratefully acknowledged for assistance with the principal component analysis.
1980 REVIEW
.
PR/NC/PAL COMPONENT 2 -08
-08 -04 00 04 08
-04
00
04
0.8
Figure 2. Principal component 2 versus principal component 3. Positive values of principal component 2 indicate the importance of Planulina wuellerstorfi, rare species (s 3 percent), Globocassiduilna subglobo.a, and Astrononion echolsL Negative values indicate the importance of Epistominella umbonifera. Positive values of principal component 3 indicate the importance of Epistominella exiqua6 P. wuellerstorfl, and Puelienla buioidss. Negative values indicate the dominance of G.. subglobosa.
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