Biostratigraphic correlations and regional erosion shown by the
103, permitting stratigraphic correlation. Core 109 contains nannofossil ooze of middle to late Miocene age and is unconformably overlain by Quaternary diatomaceous and muddy diatomaceous oozes. The remaining cores shown in figure 3 are Quaternary in age. Predictable changes in lithology are found in the progression from north to south along traverses E-E', F-F, and C-C'. In the deeper part of the Argentine Basin, the sediment consists of pelagic clay (cores 117, 116, and 115). Farther south are primarily diatomaceous ooze and muddy diatomaceous ooze (cores 114, 112, and 111). Less deep, and in the vicinity of the Mid-Atlantic Ridge, are to be found a calcareous diatomaceous ooze (core 76) and a unit of nannofossil ooze (core 80). Although the rest of the cores are primarily diatomaceous ooze, local variations do occur. For example, the sediments of cores 89, 90, and 91, near the America-Antarctic Ridge, contain volcanic ash, lapilli, pebbles, and sedimentary clasts. Unconformities can be observed in several cores. We wish to acknowledge the assistance and advice of Dennis Cassidy in the preparation of this article. Steve KnUttel helped in preparing the figures, which were drafted by Rosemarie Raymond and photographed by Dennis Cassidy. Funding for
Biostratigraphic correlations and regional erosion shown by the
radiolarian Cycladophora davisiana and the diatoms Eucampia balaustium and Hemidiscus karstenll R. SHELTON GRAVES Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
To conduct sedimentological studies of upper Brunhes southern ocean sediments, it is necessary to use high-resolution biostratigraphic schemes. Three biostratigraphically useful species for the interval 195,000 years before present to recent are the radiolarian Cycladophora davisiana and the diatoms Eucampia balaustium and Hemidiscus karstenii. This article describes their utility in biostratigraphic work with USNS Eltanin piston cores from the southeast Indian Ocean (for core locations, see table). The last-abundant-appearance datum (LAAD) of Hemidiscus karstenii has been dated at 195,000 years before present (Burckle, Clarke, and Shackleton 1978). This datum is of marginal utility in the present study, however. Although the datum was well established in cores E49-3, E49-24 (although somewhat stratigraphically high), and E50-9, in cores E50-10, E50-16, and E49-16, the maximum abundance of Hemidiscus karstenii is less than 4 percent. In these situations, extreme care must be exercised in 1982 REVIEW
this work has been provided by National Science Foundation contract c-1059.
References Ciesielski, P. F., and Wise, S. W., Jr. 1977. Basal sediment ages of Islas Orcadas cruise 7 piston cores. Antarctic Journal of the U.S., 12(4), 70-72. Ciesielski, P. F., Ledbetter, M. T., and Ellwood, B. B. 1982. The development of antarctic glaciation and the Neogene paleoenvironment of the Maurice Ewing Bank. Marine Geology, 46, 1-51. Jones, S. C., Wise, S. W., Jr., DeFelice, DR., Hattner, J. G., Mostajo, E. L., Gombos, A. M., and Weaver, F. M. 1979. Basal sediment ages of ARA Islas Orcadas cruise 16 piston cores. Antarctic Journal of the U.S., 14(5),151-153.
Kaharoeddin, F. A., Graves, R. S., Bergen, J. A., Eggers, M. R., Harwood, D. M., Humphreys, C. L., Goldstein, E. H., Jones, S. C., and Watkins, D. K. 1982. ARA Islas Orcadas cruise 1678 sediment descriptions (Contribution 50). Tallahassee: Florida State University, Department of Geology, Sedimentology Research Laboratory. Wise, S. W., Jr., Jones, S. C., Ciesielski, P. F., Georgi, D. T., Woodroffe, D. S., and Jacobs, S. S. 1978. Islas Orcadas cruise 16. Antarctic Journal of the U. S., 13(4), 92-94.
interpretation, because faulty slide preparation, erroneous counting, and so forth may result in a "LAAD" being indicated when in fact one is not present. In cores E50-6 and E50-12, no LAAD of Hemidiscus karstenii could be detected. A stratigraphy based on the relative abundances of the radiolarian Cycladophora davisiana, one that can be correlated with the oxygen isotope stratigraphy for the last 150,000 years, was proposed by Hays and associates (1976). Their stratigraphy was extended to 500,000 years before present by Williams and Keany (1978). These and other studies (Morley and Hays 1979; Weaver 1979) show low abundances of this radiolarian in recent sediments, followed by an acme estimated to be at 18,000 years before present (Hays et al. 1976). From this acme (interval b), abundances of C. davisiana generally decrease in older sediments to interval e3, estimated to be at 125,000 years before present (Hays et al. 1976). In the present study, the C. davisiana stratigraphy is well developed in four cores—E49-3, E49-24, E50-9, and E49-16 (figure
Piston core locations Piston core number Latitude (S)
Longitude (E)
E49-3 E49-16 E49-24 E50-6
45006.4' 5026.0' 470593 48001.6'
10954.9 9010.6' 9502.2' 10514.6'
E50-9 E50-10 E50-12 E50-16
5201.3' 53058.7' 57057.2' 6102.6'
105000.6' 104056.2' 105001.0' 11448.8'
139
1)—with intervals a–e 3 being clearly recognizable except where interval a is missing. The other cores in which this stratigraphy was attempted (E50-6, E50-12, and E50-16) are missing sediments from intervals a–e. Another species whose downcore abundance fluctuations provide the basis of a useful stratigraphy is the diatom Eucampia balaustium (Clarke, Burckle, and Morley 1979). However, caution must be exercised in interpreting these abundance patterns. Where currents are strong, the large size and the robustness of this diatom may cause it to form a lag deposit that is not truly representative of its actual abundance (Kellogg, Truesdale, and Osterman 1979). The downcore fluctuations of E. balaustium, designated as intervals a–g, have been correlated with the oxygen isotope stratigraphy for the last 190,000 years (Weaver 1979). In the present study, the E. balaustium stratigraphy is well developed in four cores (E49-3, E49-24, E49-16, and E50-9; figure 2), with
49-3 49-24 0cm-
0% 0% 0% 0% 20%
50-9
0% 10% 20% 30% 40%
major abundance increases at intervals b and f and a smaller abundance increase at interval d. Intervals c and e, which are abundance minima, are somewhat more difficult to discern, especially for cores that have high sedimentation rates. In cores E50-6, E50-10, E50-12, and E50-16, however, the first intervals encountered were f or g, due to the fact that younger sediments are missing. Several authors (e.g., Watkins and Kennett 1971) have given evidence of numerous unconformities in the southeast Indian Ocean, caused by swiftly moving and still active currents (Kolla et al. 1976). This study reaffirms the importance of current activity in this area, since sediments younger than stage f in cores E50-16, E50-12, E50-10, and E50-9 are missing. A glance at a core location map (Cassidy et al. 1977) shows that the geographic spread of these cores is regional in extent. Clearly, this area is affected by swiftly moving currents, most likely caused by eastward-flowing bottom water (Kolla et al. 1976).
50-12
50-6
0% 0% 0% 0% 20% 30% 40%
49-16
50-16
0% 0% 20% 30% 0% 0%
100— d
e 2 e e 3 e3 200-
300-
400-
500-
600 —
e2
e3
800
900
Figure 1. Cycladophora davisiana stratigraphy. C. davisiana appears to reach a peak at about 18,000 years before present and a low at about 125,000 years before present (interval e3).
140
ANTARCTIC JOURNAL
49-3 49-24
50-9
49-16
50-6
50-10 50-12
0% 0% 0% 0% 20% % 0% 20% 30% 0% 10% 20% 30% 0% 0% 0cm' _
g (?)
I
50-16
10% 20% 30% 0% 10%
10% 20% 30% 40% 0%
i
d
400
LAAD of Hem/discus korsten//
500
600
800
900 -
Figure 2. Eucampla balaustlum stratigraphy. Interval b, which marks a major increase in abundance, is dated at about 13,000 to 15,000 years before present. The last-abundant-appearance data (LAAD) for Hemisdiscus karstenil is dated at 195,000 years before present.
References Burckle, L. H., Clarke, D. B., and Shackleton, N. J . 1978. Isochronous last-abundant-appearance datum (LAAD) of the diatom Hemidiscus karstenii in the sub-Antarctic. Geology, 6, 243-246. Cassidy, D. S., Kaharoeddin, F. A., Zemmels, I., and Knapp, M. B. 1977. USNS Eltanin: An inventory of core location data, with core location maps and cruise 55 core descriptions (Contribution 44). Tallahassee: Florida State University, Department of Geology, Sedimentology Research Laboratory. Clarke, D. B., Burckle, L. H., and Morley, J . 1979. Abundance distribution of Eucampia balaustium and Hemidiscus karstenii in the late Pleistocene of the southern ocean—Stratigraphic and paleoclimatic implications. EOS, Transactions of the American Geophysical Union,
60(18), 273. (Abstract) Hays, J. D., Lozano, J . A., Shackleton, N. J . , and Irving, G. 1976. Reconstruction of the Atlantic and western Indian Ocean sectors of the 18,000 B.P. antarctic ocean. In R. M. Cline and J . D. Hays (Eds.), Investigation of late Quaternary paleoceanography and paleoclimatology
(Memoir 145). Tulsa, Okla.: Geological Society of America.
1982 REVIEW
Kellogg, T. B., Truesdale, R. S., and Osterman, L. E. 1979. Late Quaternary extent of the west antarctic ice sheet: New evidence from Ross Sea cores. Geology, 7(5), 249-253. Kolla, V., Sullivan, L., Streeter, S. S., and Langseth, M. G., Jr. 1976. Spreading of antarctic bottom water and its effects on the floor of the Indian Ocean inferred from bottom-water potential temperature, turbidity and sea-floor photography. Marine Geology, 21, 171-189. Morley, J . J. , and Hays, J . D. 1979. Cycladophora davisiana: A stratigraphic tool for Pleistocene North Atlantic and interhemispheric correlation. Earth and Planetary Science Letters, 44, 383-389. Watkins, N. D., and Kennett, J . P. 1971. Antarctic bottom water: Major change in velocity during the late Cenozoic between Australia and Antarctica. Science, 173, 813-817. Weaver, M. T. 1979. Late Quaternary paleoclimatic and paleoglacial history of the southwest Pacific subantarctic and antarctic region: Analysis of a glacial cycle. Unpublished master's thesis, Florida State University.
Williams, D. F., and Keany, J . 1978. Comparison of radiolarian/ planktonic foraminiferal paleoceanography of the subantarctic Indian Ocean. Quaternary Research, 9(1), 71-86.
141
Biostratigraphic correlations and regional erosion shown by the
radiolarian Cycladophora davisiana and the diatoms Eucampia balaustium and Hemidiscus karstenll R. SHELTON GRAVES Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
To conduct sedimentological studies of upper Brunhes southern ocean sediments, it is necessary to use high-resolution biostratigraphic schemes. Three biostratigraphically useful species for the interval 195,000 years before present to recent are the radiolarian Cycladophora davisiana and the diatoms Eucampia balaustium and Hemidiscus karstenii. This article describes their utility in biostratigraphic work with USNS Eltanin piston cores from the southeast Indian Ocean (for core locations, see table). The last-abundant-appearance datum (LAAD) of Hemidiscus karstenii has been dated at 195,000 years before present (Burckle, Clarke, and Shackleton 1978). This datum is of marginal utility in the present study, however. Although the datum was well established in cores E49-3, E49-24 (although somewhat stratigraphically high), and E50-9, in cores E50-10, E50-16, and E49-16, the maximum abundance of Hemidiscus karstenii is less than 4 percent. In these situations, extreme care must be exercised in 1982 REVIEW
this work has been provided by National Science Foundation contract c-1059.
References Ciesielski, P. F., and Wise, S. W., Jr. 1977. Basal sediment ages of Islas Orcadas cruise 7 piston cores. Antarctic Journal of the U.S., 12(4), 70-72. Ciesielski, P. F., Ledbetter, M. T., and Ellwood, B. B. 1982. The development of antarctic glaciation and the Neogene paleoenvironment of the Maurice Ewing Bank. Marine Geology, 46, 1-51. Jones, S. C., Wise, S. W., Jr., DeFelice, DR., Hattner, J. G., Mostajo, E. L., Gombos, A. M., and Weaver, F. M. 1979. Basal sediment ages of ARA Islas Orcadas cruise 16 piston cores. Antarctic Journal of the U.S., 14(5),151-153.
Kaharoeddin, F. A., Graves, R. S., Bergen, J. A., Eggers, M. R., Harwood, D. M., Humphreys, C. L., Goldstein, E. H., Jones, S. C., and Watkins, D. K. 1982. ARA Islas Orcadas cruise 1678 sediment descriptions (Contribution 50). Tallahassee: Florida State University, Department of Geology, Sedimentology Research Laboratory. Wise, S. W., Jr., Jones, S. C., Ciesielski, P. F., Georgi, D. T., Woodroffe, D. S., and Jacobs, S. S. 1978. Islas Orcadas cruise 16. Antarctic Journal of the U. S., 13(4), 92-94.
interpretation, because faulty slide preparation, erroneous counting, and so forth may result in a "LAAD" being indicated when in fact one is not present. In cores E50-6 and E50-12, no LAAD of Hemidiscus karstenii could be detected. A stratigraphy based on the relative abundances of the radiolarian Cycladophora davisiana, one that can be correlated with the oxygen isotope stratigraphy for the last 150,000 years, was proposed by Hays and associates (1976). Their stratigraphy was extended to 500,000 years before present by Williams and Keany (1978). These and other studies (Morley and Hays 1979; Weaver 1979) show low abundances of this radiolarian in recent sediments, followed by an acme estimated to be at 18,000 years before present (Hays et al. 1976). From this acme (interval b), abundances of C. davisiana generally decrease in older sediments to interval e3, estimated to be at 125,000 years before present (Hays et al. 1976). In the present study, the C. davisiana stratigraphy is well developed in four cores—E49-3, E49-24, E50-9, and E49-16 (figure
Piston core locations Piston core number Latitude (S)
Longitude (E)
E49-3 E49-16 E49-24 E50-6
45006.4' 5026.0' 470593 48001.6'
10954.9 9010.6' 9502.2' 10514.6'
E50-9 E50-10 E50-12 E50-16
5201.3' 53058.7' 57057.2' 6102.6'
105000.6' 104056.2' 105001.0' 11448.8'
139
1)—with intervals a–e 3 being clearly recognizable except where interval a is missing. The other cores in which this stratigraphy was attempted (E50-6, E50-12, and E50-16) are missing sediments from intervals a–e. Another species whose downcore abundance fluctuations provide the basis of a useful stratigraphy is the diatom Eucampia balaustium (Clarke, Burckle, and Morley 1979). However, caution must be exercised in interpreting these abundance patterns. Where currents are strong, the large size and the robustness of this diatom may cause it to form a lag deposit that is not truly representative of its actual abundance (Kellogg, Truesdale, and Osterman 1979). The downcore fluctuations of E. balaustium, designated as intervals a–g, have been correlated with the oxygen isotope stratigraphy for the last 190,000 years (Weaver 1979). In the present study, the E. balaustium stratigraphy is well developed in four cores (E49-3, E49-24, E49-16, and E50-9; figure 2), with
49-3 49-24 0cm-
0% 0% 0% 0% 20%
50-9
0% 10% 20% 30% 40%
major abundance increases at intervals b and f and a smaller abundance increase at interval d. Intervals c and e, which are abundance minima, are somewhat more difficult to discern, especially for cores that have high sedimentation rates. In cores E50-6, E50-10, E50-12, and E50-16, however, the first intervals encountered were f or g, due to the fact that younger sediments are missing. Several authors (e.g., Watkins and Kennett 1971) have given evidence of numerous unconformities in the southeast Indian Ocean, caused by swiftly moving and still active currents (Kolla et al. 1976). This study reaffirms the importance of current activity in this area, since sediments younger than stage f in cores E50-16, E50-12, E50-10, and E50-9 are missing. A glance at a core location map (Cassidy et al. 1977) shows that the geographic spread of these cores is regional in extent. Clearly, this area is affected by swiftly moving currents, most likely caused by eastward-flowing bottom water (Kolla et al. 1976).
50-12
50-6
0% 0% 0% 0% 20% 30% 40%
49-16
50-16
0% 0% 20% 30% 0% 0%
100— d
e 2 e e 3 e3 200-
300-
400-
500-
600 —
e2
e3
800
900
Figure 1. Cycladophora davisiana stratigraphy. C. davisiana appears to reach a peak at about 18,000 years before present and a low at about 125,000 years before present (interval e3).
140
ANTARCTIC JOURNAL
49-3 49-24
50-9
49-16
50-6
50-10 50-12
0% 0% 0% 0% 20% % 0% 20% 30% 0% 10% 20% 30% 0% 0% 0cm' _
g (?)
I
50-16
10% 20% 30% 0% 10%
10% 20% 30% 40% 0%
i
d
400
LAAD of Hem/discus korsten//
500
600
800
900 -
Figure 2. Eucampla balaustlum stratigraphy. Interval b, which marks a major increase in abundance, is dated at about 13,000 to 15,000 years before present. The last-abundant-appearance data (LAAD) for Hemisdiscus karstenil is dated at 195,000 years before present.
References Burckle, L. H., Clarke, D. B., and Shackleton, N. J . 1978. Isochronous last-abundant-appearance datum (LAAD) of the diatom Hemidiscus karstenii in the sub-Antarctic. Geology, 6, 243-246. Cassidy, D. S., Kaharoeddin, F. A., Zemmels, I., and Knapp, M. B. 1977. USNS Eltanin: An inventory of core location data, with core location maps and cruise 55 core descriptions (Contribution 44). Tallahassee: Florida State University, Department of Geology, Sedimentology Research Laboratory. Clarke, D. B., Burckle, L. H., and Morley, J . 1979. Abundance distribution of Eucampia balaustium and Hemidiscus karstenii in the late Pleistocene of the southern ocean—Stratigraphic and paleoclimatic implications. EOS, Transactions of the American Geophysical Union,
60(18), 273. (Abstract) Hays, J. D., Lozano, J . A., Shackleton, N. J . , and Irving, G. 1976. Reconstruction of the Atlantic and western Indian Ocean sectors of the 18,000 B.P. antarctic ocean. In R. M. Cline and J . D. Hays (Eds.), Investigation of late Quaternary paleoceanography and paleoclimatology
(Memoir 145). Tulsa, Okla.: Geological Society of America.
1982 REVIEW
Kellogg, T. B., Truesdale, R. S., and Osterman, L. E. 1979. Late Quaternary extent of the west antarctic ice sheet: New evidence from Ross Sea cores. Geology, 7(5), 249-253. Kolla, V., Sullivan, L., Streeter, S. S., and Langseth, M. G., Jr. 1976. Spreading of antarctic bottom water and its effects on the floor of the Indian Ocean inferred from bottom-water potential temperature, turbidity and sea-floor photography. Marine Geology, 21, 171-189. Morley, J . J. , and Hays, J . D. 1979. Cycladophora davisiana: A stratigraphic tool for Pleistocene North Atlantic and interhemispheric correlation. Earth and Planetary Science Letters, 44, 383-389. Watkins, N. D., and Kennett, J . P. 1971. Antarctic bottom water: Major change in velocity during the late Cenozoic between Australia and Antarctica. Science, 173, 813-817. Weaver, M. T. 1979. Late Quaternary paleoclimatic and paleoglacial history of the southwest Pacific subantarctic and antarctic region: Analysis of a glacial cycle. Unpublished master's thesis, Florida State University.
Williams, D. F., and Keany, J . 1978. Comparison of radiolarian/ planktonic foraminiferal paleoceanography of the subantarctic Indian Ocean. Quaternary Research, 9(1), 71-86.
141
