Water mass-related morphologic variation in the Globigerina bulloides ...
nformity, with the upper positive skew reflecting e decrease of velocity associated with the end of e pulse. Other factors that affect the textural trameters include compositional variation. We [all discuss these in detail elsewhere and show at bottom currents are the dominant control of xtural variations. The present distribution of stronger bottom irrents coincides roughly to the location of the resent Antarctic Convergence (Gordon, 1971), hich is also associated with the present distriution of manganese nodules (Goodell, 1973). )ur inferred bottom current pulses suggest that is region may have been 5° of latitude wider uring the Lower Matuyama (figure 1). This research was supported by National Science Foundation grant DES 75-04877.
References Blatt, H., G. Middleton, and R. Murray. 1972. Origin of Sedimentary Rocks. Englewood Cliffs, Prentice-Hall. 634p. Goode!!, H. G. 1973. The sediments. Antarctic Map Folio Series, 17: 1-9. Gordon, A. L. 1971. Oceanography of antarctic water. Antarctic Research Series, 15: 169-203. Huang, T. C., and N. D. Watkins. 1975. Sedimentological evidence for increased bottom currents in the Pacific sector of the southern ocean during the Matuyama Epoch. EOS, Transactions of the American Geophysical Union, 56: 384 (abstract). Huang, T. C., and N. D. Watkins. In press. Variations in Antarctic Bottom Water velocities recorded by deep sea sediments in the southern ocean. Deep Sea Research. Huang, T. C., N. D. Watkins, and D. M. Shaw. 1975. Atmospherically transported volcanic glass in deep-sea sediments: volcanism in subantarctic latitudes of the South Pacific during the Upper Pliocene and Pleistocene. Geological Society ofAmertca. Bulletin, 86:1305-1315. Kennett, J . P., and N. D. Watkins. 1975. Deep-sea erosion and manganese nodule development in the southeast Indian Ocean. Science, 188: 1011-1013. Kennett, J . P., R. E. Burns, J . E. Andrews, M. Churkmijun, T. A. Davies, P. Dumitriac, A. R. Edwards, J . S. Galehouse, G. H. Packham, and G. J. vander Lingen. 1972. Australiaantarctic continental drift, paleocirculation changes, and Oligocene deep-sea erosion. Nature Physical Science, 239: 5155. Kennett, J . P., R. E. Houtz, P. B. Andrews, A. R. Edwards, V. A. Gostin, M. Hajos, M. Hampton, D. G. Jenkins, S. V. Margolis, A. T. Ovenshine, and K. Perch-Nielsen. 1975. Cenozoic paleoceanography in the southwest Pacific Ocean, antarctic glaciation, and the development of the circumantarctic current. In: Initial Reports of the Deep-Sea Drilling Project (Government Printing Office, Washington, D.C.) 26: 1155-1169. Krumbein, S. C., and E. J . Aberdeen. 1937. The sediments of Barataria Bay.Journal of Sedimentary Petrology, 7: 3-17. Watkins, N. D., and J . P. Kennett. 1971. Antarctic Bottom Water: major change in velocity during the Late Cenozoic between Australia and Antarctica. Science, 173: 813-818.
September/October 1975
Watkins, N. D., and J . P. Kennett. 1972. Regional sedimentary disconformities and Upper Cenozoic changes in bottom water velocities between Australia and Antarctica. Antarctic Research Series, 19: 272-294.
Water mass-related morphologic variation in the Globigerina bulloides plexus in the Recent southern Indian Ocean and JAMES P. KENNETT Graduate School of Oceanography University of Rhode Island Kingston, Rhode Island 02881
BJORN MALMGREN
We are making biometric analyses of the planktonic foraminifera Globigerina bulloides d'OrbignyG.falconensis Blow plexus in trigger core tops (Ellanin cruises 44, 45, 48, 49, and 50) from subantarctic and southern subtropical areas of the southern Indian Ocean (30° to 53°S.). The analyses include the following: frequency, coiling direction, general size, apertural size, and shape variation. We are analyzing this group biometrically in an attempt to understand the biogeography especially with regard to water mass boundaries, to differentiate phenotypically controlled from genetically controlled variation, and to establish indices for future paleoceanographic use. Preliminary results indicate that a close correspondence exists between water mass distribution and frequency variations and certain morphological features of G. bulloides. Specimens referable to G. bulloides predominate the entire latitudinal range except in a few of the northernmost samples where G.falionensis is dominant (figure, A). The proportion of G. bulloides within the plexus is 92 to 100 percent in subpolar waters and 46 to 79 percent in subtropical waters. A distinct pattern also exists in the coiling characteristics in G. bulloides, with increased sinistral coiling forms occurring from north to south (figure, B). The frequencies of sinistral forms are 57 to 68 percent in subtropical waters and 63 to 71 percent in subpolar and northern polar waters. The correlation between latitude and coiling is statistically significant at the 1 percent level (the Kendall coef261
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•• 55 2501 50S 45'S 40'S 35'S 30'S 50'S 45'S 40'S 35'S 30'S 50'S 45'S 400 S 350S 30'SLATITUDE LATITUDE LATITUDE Latitudinal variation in the southern Indian Ocean. A: percentage of Globigerina bulloides in relation to total number of specimens of the G. bulloides-G. falconensis complex. B: percentage of sinistrally coiled G. bulloides. C: average test length of G. bulloides.
ficient of rank correlation is 0.53). This correlation agrees with a relationship between surface water temperatures and coiling of modern G. bulloides in plankton samples from the southwestern Atlantic Ocean observed by Boltovskoy (1973). Coiling of G. falconensis is not related to latitude. The average test size of G. bulloides generally increases toward the south as indicated by a rank correlation of 0.59, which is significant at the 0.1 percent level (figure, Q. Values for the test length generally vary between 248 and 322 microns in waters south of this latitude. The relative morphological variability measured by the coefficient of variation is greater in polar and subpolar areas than in the subtropics. This variability is caused by an association of large and small specimens in the southern areas. In more northern areas large specimens are absent, resulting in a smaller relative variation. G. falconensis is normally smaller than G. bulloides, with mean test lengths ranging between 249 and 288 microns. The apertural size (height and width) is highly positively correlated with the size of the test in both species. Therefore, the apertural sizes show a trend similar to that of the general sizes. The rank correlation between mean apertural height and latitude in G. bulloides is 0.51 (significant at the 1 percent level) with values varying between 38 and 67 microns in areas north of 45°S., and between 65 and 105 microns in area south of this latitude. The apertural size of G. falconensis shows no latitudinal relationship. Principal component analysis of 13 test dimensions (including general size of the test, apertural size, and chamber dimensions) shows that the complexity of the morphologic variability in the entire test of G. bulloides is greater in subtropical waters 262
than in subpolar and polar waters. The first principal component extracts a size factor that accounts for between 80 and 88 percent of the variation in the 13-dimensional space in the subpolar and polar samples, and for between 57 and 81 percent in the subtropical samples. The second principal component is a "kummerform" factor, which reflects the morphological variations resulting from a reduced final chamber. The distinct difference in morphologic complexity at different latitudes to a great extent reflects higher frequency of kummerforms in northern waters. The kummerform factor normally accounts for a greater portion of the variance in G.falconensis, indicating that kummerform specimens are more common in this species than in G. bulloides. Forthcoming extensions of the project will include multivariate biometrical analyses of the heterogeneity of the morphologic variation within the G. bulloides-G.falconensis complex, the establishment of discriminant functions aiming at optimal differentiation between the two species, and attempts at paleoclimatic utilization of observed trends in a piston core from near the Subtropical Convergence. This research was supported by National Science Foundation grant o pp 75-15511. References Boltovskoy, E. 1973. Note on the determination of absolute surface water paleotemperature by means of the foraminifer Giobigeiina bulloides d'Orbigny. Paläontologische Zeitschrift, 47: 152-155. ANTARCTIC JOURNAL
References Blatt, H., G. Middleton, and R. Murray. 1972. Origin of Sedimentary Rocks. Englewood Cliffs, Prentice-Hall. 634p. Goode!!, H. G. 1973. The sediments. Antarctic Map Folio Series, 17: 1-9. Gordon, A. L. 1971. Oceanography of antarctic water. Antarctic Research Series, 15: 169-203. Huang, T. C., and N. D. Watkins. 1975. Sedimentological evidence for increased bottom currents in the Pacific sector of the southern ocean during the Matuyama Epoch. EOS, Transactions of the American Geophysical Union, 56: 384 (abstract). Huang, T. C., and N. D. Watkins. In press. Variations in Antarctic Bottom Water velocities recorded by deep sea sediments in the southern ocean. Deep Sea Research. Huang, T. C., N. D. Watkins, and D. M. Shaw. 1975. Atmospherically transported volcanic glass in deep-sea sediments: volcanism in subantarctic latitudes of the South Pacific during the Upper Pliocene and Pleistocene. Geological Society ofAmertca. Bulletin, 86:1305-1315. Kennett, J . P., and N. D. Watkins. 1975. Deep-sea erosion and manganese nodule development in the southeast Indian Ocean. Science, 188: 1011-1013. Kennett, J . P., R. E. Burns, J . E. Andrews, M. Churkmijun, T. A. Davies, P. Dumitriac, A. R. Edwards, J . S. Galehouse, G. H. Packham, and G. J. vander Lingen. 1972. Australiaantarctic continental drift, paleocirculation changes, and Oligocene deep-sea erosion. Nature Physical Science, 239: 5155. Kennett, J . P., R. E. Houtz, P. B. Andrews, A. R. Edwards, V. A. Gostin, M. Hajos, M. Hampton, D. G. Jenkins, S. V. Margolis, A. T. Ovenshine, and K. Perch-Nielsen. 1975. Cenozoic paleoceanography in the southwest Pacific Ocean, antarctic glaciation, and the development of the circumantarctic current. In: Initial Reports of the Deep-Sea Drilling Project (Government Printing Office, Washington, D.C.) 26: 1155-1169. Krumbein, S. C., and E. J . Aberdeen. 1937. The sediments of Barataria Bay.Journal of Sedimentary Petrology, 7: 3-17. Watkins, N. D., and J . P. Kennett. 1971. Antarctic Bottom Water: major change in velocity during the Late Cenozoic between Australia and Antarctica. Science, 173: 813-818.
September/October 1975
Watkins, N. D., and J . P. Kennett. 1972. Regional sedimentary disconformities and Upper Cenozoic changes in bottom water velocities between Australia and Antarctica. Antarctic Research Series, 19: 272-294.
Water mass-related morphologic variation in the Globigerina bulloides plexus in the Recent southern Indian Ocean and JAMES P. KENNETT Graduate School of Oceanography University of Rhode Island Kingston, Rhode Island 02881
BJORN MALMGREN
We are making biometric analyses of the planktonic foraminifera Globigerina bulloides d'OrbignyG.falconensis Blow plexus in trigger core tops (Ellanin cruises 44, 45, 48, 49, and 50) from subantarctic and southern subtropical areas of the southern Indian Ocean (30° to 53°S.). The analyses include the following: frequency, coiling direction, general size, apertural size, and shape variation. We are analyzing this group biometrically in an attempt to understand the biogeography especially with regard to water mass boundaries, to differentiate phenotypically controlled from genetically controlled variation, and to establish indices for future paleoceanographic use. Preliminary results indicate that a close correspondence exists between water mass distribution and frequency variations and certain morphological features of G. bulloides. Specimens referable to G. bulloides predominate the entire latitudinal range except in a few of the northernmost samples where G.falionensis is dominant (figure, A). The proportion of G. bulloides within the plexus is 92 to 100 percent in subpolar waters and 46 to 79 percent in subtropical waters. A distinct pattern also exists in the coiling characteristics in G. bulloides, with increased sinistral coiling forms occurring from north to south (figure, B). The frequencies of sinistral forms are 57 to 68 percent in subtropical waters and 63 to 71 percent in subpolar and northern polar waters. The correlation between latitude and coiling is statistically significant at the 1 percent level (the Kendall coef261
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•• 55 2501 50S 45'S 40'S 35'S 30'S 50'S 45'S 40'S 35'S 30'S 50'S 45'S 400 S 350S 30'SLATITUDE LATITUDE LATITUDE Latitudinal variation in the southern Indian Ocean. A: percentage of Globigerina bulloides in relation to total number of specimens of the G. bulloides-G. falconensis complex. B: percentage of sinistrally coiled G. bulloides. C: average test length of G. bulloides.
ficient of rank correlation is 0.53). This correlation agrees with a relationship between surface water temperatures and coiling of modern G. bulloides in plankton samples from the southwestern Atlantic Ocean observed by Boltovskoy (1973). Coiling of G. falconensis is not related to latitude. The average test size of G. bulloides generally increases toward the south as indicated by a rank correlation of 0.59, which is significant at the 0.1 percent level (figure, Q. Values for the test length generally vary between 248 and 322 microns in waters south of this latitude. The relative morphological variability measured by the coefficient of variation is greater in polar and subpolar areas than in the subtropics. This variability is caused by an association of large and small specimens in the southern areas. In more northern areas large specimens are absent, resulting in a smaller relative variation. G. falconensis is normally smaller than G. bulloides, with mean test lengths ranging between 249 and 288 microns. The apertural size (height and width) is highly positively correlated with the size of the test in both species. Therefore, the apertural sizes show a trend similar to that of the general sizes. The rank correlation between mean apertural height and latitude in G. bulloides is 0.51 (significant at the 1 percent level) with values varying between 38 and 67 microns in areas north of 45°S., and between 65 and 105 microns in area south of this latitude. The apertural size of G. falconensis shows no latitudinal relationship. Principal component analysis of 13 test dimensions (including general size of the test, apertural size, and chamber dimensions) shows that the complexity of the morphologic variability in the entire test of G. bulloides is greater in subtropical waters 262
than in subpolar and polar waters. The first principal component extracts a size factor that accounts for between 80 and 88 percent of the variation in the 13-dimensional space in the subpolar and polar samples, and for between 57 and 81 percent in the subtropical samples. The second principal component is a "kummerform" factor, which reflects the morphological variations resulting from a reduced final chamber. The distinct difference in morphologic complexity at different latitudes to a great extent reflects higher frequency of kummerforms in northern waters. The kummerform factor normally accounts for a greater portion of the variance in G.falconensis, indicating that kummerform specimens are more common in this species than in G. bulloides. Forthcoming extensions of the project will include multivariate biometrical analyses of the heterogeneity of the morphologic variation within the G. bulloides-G.falconensis complex, the establishment of discriminant functions aiming at optimal differentiation between the two species, and attempts at paleoclimatic utilization of observed trends in a piston core from near the Subtropical Convergence. This research was supported by National Science Foundation grant o pp 75-15511. References Boltovskoy, E. 1973. Note on the determination of absolute surface water paleotemperature by means of the foraminifer Giobigeiina bulloides d'Orbigny. Paläontologische Zeitschrift, 47: 152-155. ANTARCTIC JOURNAL
