Correlation of planktonic foraminiferal curves from ...
cate evolutionary trends and/or response of this species to environmental stresses. Spaciotem poral modification will be compared with late Cretaceous oceanographic and climatic changes discussed by Worsley (1971) to detect possible correlation. This research was supported by National Science Foundation grant o pp 74-20109. References Deflandre, G. 1959. Sur les nanofossiles calcaires et leur systématique. Revue de Mzcropaleontologie, 2(3): 127-152. Wind, F. H. 1975. Affinity of Lucianorhabdus and species of Tetralithus in late Cretaceous Gulf Coast samples. Transactions of the Gulf Coast Association of Geological Societies, 25: 350-361. Wind, F. H., and S. W. Wise, Jr. 1975. High latitude late Cretaceous nanoplankton biostratigraphy (abstract). Geological Society of America. Abstracts with programs, 7(7): 1320. Worsley, T. R. 1971. The Cretaceous-Tertiary boundary event in the ocean. In: Studies in Paleo-Oceanography (Hay, W. W., editor). Society for Economic Paleontology and Mineralogy. Special publication, 20: 94-125.
Correlation of planktonic foraminiferal curves from southeast Indian Ocean sediments using oxygen isotope stratigraphy DOUGLAS
F. WILLIAMS
Graduate School of Oceanography University of Rhode Island Kingston, Rhode Island 02881
Little is known about the magnitude and the tim ing of major water-mass movements in the southeast Indian Ocean over the last 500,000 years. Faunal analyses of planktonic foraminifera in five piston cores (Eltanin cruise 48) taken beneath the present subtropical convergence and at the boundary of transitional and northern subantarctic water masses reveal a consistent pattern in the faunal changes. Since planktonic foraminifera are sensitive to certain water-mass properties, faunal changes in the fossil assemblages should reflect changes in water-mass positions. Determining if these water-mass changes are synchronous worldwide is critical to discovering what driving mechanisms are responsible for long-term, global 268
climatic changes characteristic of the Pleistocene. Paleomagnetic stratigraphy of deep-sea sediments with micropaleontological control has been important in testing the synchronous nature of events recorded by microfossils in deep-sea sediments. However, the timing of events within the Brunhes Epoch must be extrapolated from the BrunhesMatuyama boundary. Oxygen isotope stratigraphy independently dated by paleomagnetic stratigraphy (Shackleton and Opdyke, 1973) and thorium/uranium dating (Broecker and van Donk, 1970) now can be applied confidently to deep-sea sediments and associated events within the last 700,000 years. Three methods were used to infer the watermass changes: coiling ratio of Neogloboquadrina pachyderma; a total faunal index composed of transi tional and subantarctic assemblages; sea surface temperature estimates based on a steady decrease in species diversity of Recent planktonic foraminifera with latitude (Williams and Johnson, 1975). The consistency obtained by all three methods in each of the cores is illustrated in a plot for core E48-22 (figure 0. Oxygen isotope analyses of Gbborotalia truncatulinoides in core E48-22 through glacial stage 6 reveals that the faunal and temperature changes are reflected by the same changes in the oxygen is curve. The isotopic analyses were performed using a VG Micromass 602C mass spectrometer on approximately 20 specimens from each sample after phosphoric acid extraction at 50°C. Correlation of the oxygen isotope curve in E4822 through glacial stage 6 with the oxygen isotope curve and time scale in V28-238 from Shackleton and Opdyke (1973) establishes the timing of the paleoceanographic events in each of the cores (figure 2). Six major advances of the Australasian Front from 48° to 40°S. have occurred in the last 500,000 years. This study also substantiates that Gboborotalia crassaformis was replaced by G. truncatulinoides in the vicinity of 40°S. approximately 300,000 years before present, as independently dated by Kennett (1970) and by Vella and Watkins (in press) using paleomagnetic stratigraphy. I gratefully acknowledge J. P. Kennett and M. L. Bender for financial support through National Science Foundation grants o pp 71-04027 and GA37125, M. S. Sommer and R. K. Matthews for the use of the mass spectrometer at Brown University, and D. Cassidy for his assistance as curator of the Eltanjn core collection. ANTARCTIC JOURNAL
rugure 1. Lomparlson ot two taunal metnoas, sea surtace paieotemperature estimates, ana oxygen isotope curve Tor Wranin core 48-22. The same consistent patterns are obtained in cores E48-28, E48-27, E48-23, and E48-03 not shown here. The precision for each of the methods is given directly below each respective curve.
E 48-22 E48-22 V28-238 E48-03 18 80 18 LEFT PACHYDERMA TEMPERATURE so %
OC
['I
o
8 10 12 14 + + L +1 -1.0 -LU IUU DU LI) Ui
O
0 z
U) 100
U z
>200 Uj
Figure 2. Correlation for 0 06 300 the temperature and oxy- Z z gen isotope curves for E4822 and N. pachyderma coiling ratio curve for E48-03 0 400 from this study to the oxygen isotope stratigraphy and time scale of V28-238 (Shackleton and Opdyke, 500 1973). The replacement of G. crassaformis by G. truncatulinoides in sediments from E48-03 is also shown. 600 References
Broecker, W. S., and J . van Donk. 1970. Insolation changes, ice volumes and 018 record in deep-sea cores. Reviews of Geophysics and Space Physics, 8: 169-198. Kennett, J. P. 1970. Pleistocene paleoclimates and foraminiferal biostratigraphy in subantarctic deep-sea cores. Deep-Sea Research, 17: 125-140. Shackleton, N. J . , and N. D. Opdyke. 1973. Oxygen isotope
September/October 1975
LI)
0 (I)
U
0
13
and paleomagnetic stratigraphy of equatorial Pacific core V28-238: oxygen isotope temperatures and ice volumes on a 105 year and 106 year scale. Quaternary Research, 3: 39-55. Williams, D. F., and W. C. Johnson III. 1975. Diversity of Recent planktonic foraminifera in the southern Indian Ocean and Late Pleistocene paleotemperatures. Quaternary Research, 5: 237-250. Vella, P., and N. D. Watkins. In press. Middle and Late Quaternary paleomagnetism and biostratigraphy of four subantarctic deep-sea cores from southwest Australia. 0. L. Bandy Memorial Volume.
269
Correlation of planktonic foraminiferal curves from southeast Indian Ocean sediments using oxygen isotope stratigraphy DOUGLAS
F. WILLIAMS
Graduate School of Oceanography University of Rhode Island Kingston, Rhode Island 02881
Little is known about the magnitude and the tim ing of major water-mass movements in the southeast Indian Ocean over the last 500,000 years. Faunal analyses of planktonic foraminifera in five piston cores (Eltanin cruise 48) taken beneath the present subtropical convergence and at the boundary of transitional and northern subantarctic water masses reveal a consistent pattern in the faunal changes. Since planktonic foraminifera are sensitive to certain water-mass properties, faunal changes in the fossil assemblages should reflect changes in water-mass positions. Determining if these water-mass changes are synchronous worldwide is critical to discovering what driving mechanisms are responsible for long-term, global 268
climatic changes characteristic of the Pleistocene. Paleomagnetic stratigraphy of deep-sea sediments with micropaleontological control has been important in testing the synchronous nature of events recorded by microfossils in deep-sea sediments. However, the timing of events within the Brunhes Epoch must be extrapolated from the BrunhesMatuyama boundary. Oxygen isotope stratigraphy independently dated by paleomagnetic stratigraphy (Shackleton and Opdyke, 1973) and thorium/uranium dating (Broecker and van Donk, 1970) now can be applied confidently to deep-sea sediments and associated events within the last 700,000 years. Three methods were used to infer the watermass changes: coiling ratio of Neogloboquadrina pachyderma; a total faunal index composed of transi tional and subantarctic assemblages; sea surface temperature estimates based on a steady decrease in species diversity of Recent planktonic foraminifera with latitude (Williams and Johnson, 1975). The consistency obtained by all three methods in each of the cores is illustrated in a plot for core E48-22 (figure 0. Oxygen isotope analyses of Gbborotalia truncatulinoides in core E48-22 through glacial stage 6 reveals that the faunal and temperature changes are reflected by the same changes in the oxygen is curve. The isotopic analyses were performed using a VG Micromass 602C mass spectrometer on approximately 20 specimens from each sample after phosphoric acid extraction at 50°C. Correlation of the oxygen isotope curve in E4822 through glacial stage 6 with the oxygen isotope curve and time scale in V28-238 from Shackleton and Opdyke (1973) establishes the timing of the paleoceanographic events in each of the cores (figure 2). Six major advances of the Australasian Front from 48° to 40°S. have occurred in the last 500,000 years. This study also substantiates that Gboborotalia crassaformis was replaced by G. truncatulinoides in the vicinity of 40°S. approximately 300,000 years before present, as independently dated by Kennett (1970) and by Vella and Watkins (in press) using paleomagnetic stratigraphy. I gratefully acknowledge J. P. Kennett and M. L. Bender for financial support through National Science Foundation grants o pp 71-04027 and GA37125, M. S. Sommer and R. K. Matthews for the use of the mass spectrometer at Brown University, and D. Cassidy for his assistance as curator of the Eltanjn core collection. ANTARCTIC JOURNAL
rugure 1. Lomparlson ot two taunal metnoas, sea surtace paieotemperature estimates, ana oxygen isotope curve Tor Wranin core 48-22. The same consistent patterns are obtained in cores E48-28, E48-27, E48-23, and E48-03 not shown here. The precision for each of the methods is given directly below each respective curve.
E 48-22 E48-22 V28-238 E48-03 18 80 18 LEFT PACHYDERMA TEMPERATURE so %
OC
['I
o
8 10 12 14 + + L +1 -1.0 -LU IUU DU LI) Ui
O
0 z
U) 100
U z
>200 Uj
Figure 2. Correlation for 0 06 300 the temperature and oxy- Z z gen isotope curves for E4822 and N. pachyderma coiling ratio curve for E48-03 0 400 from this study to the oxygen isotope stratigraphy and time scale of V28-238 (Shackleton and Opdyke, 500 1973). The replacement of G. crassaformis by G. truncatulinoides in sediments from E48-03 is also shown. 600 References
Broecker, W. S., and J . van Donk. 1970. Insolation changes, ice volumes and 018 record in deep-sea cores. Reviews of Geophysics and Space Physics, 8: 169-198. Kennett, J. P. 1970. Pleistocene paleoclimates and foraminiferal biostratigraphy in subantarctic deep-sea cores. Deep-Sea Research, 17: 125-140. Shackleton, N. J . , and N. D. Opdyke. 1973. Oxygen isotope
September/October 1975
LI)
0 (I)
U
0
13
and paleomagnetic stratigraphy of equatorial Pacific core V28-238: oxygen isotope temperatures and ice volumes on a 105 year and 106 year scale. Quaternary Research, 3: 39-55. Williams, D. F., and W. C. Johnson III. 1975. Diversity of Recent planktonic foraminifera in the southern Indian Ocean and Late Pleistocene paleotemperatures. Quaternary Research, 5: 237-250. Vella, P., and N. D. Watkins. In press. Middle and Late Quaternary paleomagnetism and biostratigraphy of four subantarctic deep-sea cores from southwest Australia. 0. L. Bandy Memorial Volume.
269
