Correlation of Late Miocene-Early Pliocene radiolarian ...
Correlation of Late Miocene-Early Pliocene radiolarian zones to the paleomagnetic time scale FRED M. WEAVER Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
A suite of Eltanin piston cores from the southern ocean south of Australia has been examined in detail for their radiolarian fauna. These cores contain a nearly continuous sequence of Late Miocene through Early Pliocene sediments that were dated by both paleomagnetic and paleontological techniques (figure 1). The boundary between the Helothulus vema and the Theocalyptra bicornis spongothorax radiolarian RADIOLARIANJ TAX,A
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zones is correlated to the paleomagnetic time scal (figure 1). This datum falls within orjust after even "b" of the Gilbert reversed magnetic epoc] (t=4.14 to 3.90 million years before present and within the tentative Tau radiolarian zone pre viously suggested by Hays and Opdyke (1967) Chen (1975) estimated that this zonal boundar' corresponds to the Miocene/ Pliocene boundary a defined by Berggren (1973) (-5.0 million year before present—the epoch 5/Gilbert reversed mag netic boundary). Data presented herein il1ustrat that this zonal boundary is much younger that previously assumed. It does, however, approximatiI the Miocene/Pliocene boundary, but only as it ha: been defined in New Zealand (Kennett and Wat kins, 1974). The Helotholus vema/Theocalyptra bicornis songothorax zonal boundary coincides with a major fauna change throughout the southern ocean (Weaver, ir preparation) and is most likely related to the sig nificant regional warming detected by Weaver anc Ciesielski (1973, 1974) and by Ciesielski anc Weaver (1974), which occurred during the middk of the Gilbert magnetic epoch (several common!)
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1. Figure Correlation of the Late Miocene-Early PIlocene radiolarian zones of Chen (1974, 1975) to the paleomagnetic time scale. Magnetic data for E34-5 th (57°23'S. 159°59'E.) is from Kennett and Brunner (1973); E38-8 (61°48'S. 149054'E.) is from Watkins and Kennett (1972); E5028 (62°54'S. 150'41'E.) was provided by N. D. Watkins, QL University of Rhode Island. Diatom and silicoflagellate biostratigraphy of McCollum (1975) and Ciesielski (1975) was utilized to correJ late core sequences.
ANTARCTIC JOURNAL
temperature change in the antarctic seas. Geology, 2(10): 511515. Havs,J. D., and N. D. ()pdvke. 1967. Antarctic radiolaria, magnetic reversals, and climatic change. Science, 158: 1001. Kennett, j. P., and C. A. Brunner. 1973. Antarctic late Cenozoic glaciation: evidence for initiation of ice-rafting and inferred bottom water activity. Geological Societ of America Bid/elm,
84: 2043-2052.
Kennett, J . P., and N. D. Watkins. 1974. Late Miocene-Early P1i icc ne paleomagnetic stratigraphy, paleoclimat )logy, and hiostratigraphy in New Zealand. Geological Society of America
Bulletin, 85: 1385-1398.
\lc( olium, D. W. 1975. Diatom stratigraphy of the southern ocean. In: Initial Reports of the Deep Sea Drilling Project, 28: 515-571. Washington, D.C., U.S. Government Printing Oflice. ()pdyke, N. D. 1972. Paleomagnetism of deep-sea cores. Re-
viewS of Geophysics and Space Physics, 10(1): 213-249.
Watkins, N. D., and .J P. Kennett. 1972. Regional sedimentary disconforities m and tipper Cenozoic changes in bottom water velocities between Australasia and Antarctica. Antarctic Re-
o(lrch Series, 19: 273-293.
Weaver, F. M. In preparation. Antarctic radiolaria from the southeast Pacific basin, Deep Sea Drilling Project. leg 35. Weaver, F. M., and P. F. Ciesielski. 1973. Pliocene plaeocliiiatic history recorded in antarctic deep-sea cores. Geological Societ y of America Annual Meeting. Abstracts with programs.
856-857.
Veavcr, F. M., anti P. F. Ciesielski. 1974. Pliocene paleotempetatures and regional correlation, southern ocean. Antarctic
Journal
of
the U.S.. 1X(5): 251-253.
Figure 2. (1) Dendrospyris haysi. (2) Triceraspyris coronatus.
(3) Theocalyptra bicornis spongothorax. (4) Prunopyle hayesi (interior view). (5) Lithomelissa sp. c. (6) Stylatractus universus (Pliocene form). For taxonomic details, see Chen (1974, 1975) and Weaver (in preparation.)
occurring radiolarian species that become extinct at this time are illustrated in figure 2). A more detailed discussion of data presented here will be included in the Initial Reports of the Deep Sea Drilling Project, Leg 35. This research was supported by a Penrose grant from the Geological Society of America, and by National Science Foundation grant OPP 74-20109. References
Berggren, W. A. 1973. The Pliocene time scale: calibration of planktonic foraminifera and calcareous nanoplankton zones.
Nature, 243: 391-397.
Chen, P. H. 1974. Some new Tertiary radiolarians from antarctic deep-sea sediments. Micropaleontology, 20(4): 480-492. Chen, P. H. 1975. Antarctic radiolarians. In: Initial Reports of the Deep Sea Drilling Project, 28: 437-513. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F. 1975. Biostratigraphy and paleoecology of Neogene and Oligocene silicofiagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project, 28: 625-692. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F., and F. M. Weaver. 1974. Early Pliocene
September/October 1975
Oligocene unconformity in southeast Indian Ocean piston cores MELVIN J . MIYAJIMA
Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306 During Deep Sea Drilling Project (DSDP) legs 21, 26, and 29, a regional unconformity of EoceneOligocene age was noted in the southwest Pacific and south Indian oceans. The unconformity was observed as sediment disconformities or as dissolution facies barren of calcareous microfossils (Luyendyk and Davies, 1974). Examination of four USNS Eltanin piston cores (table) indicates a similar unconformity dated between late Eocene and early Oligocene age. Distinct lithologic changes across the unconformities were observed in all cores. Cores E45-16, E45-19, and E48-49, located in a basin southeast 271
A suite of Eltanin piston cores from the southern ocean south of Australia has been examined in detail for their radiolarian fauna. These cores contain a nearly continuous sequence of Late Miocene through Early Pliocene sediments that were dated by both paleomagnetic and paleontological techniques (figure 1). The boundary between the Helothulus vema and the Theocalyptra bicornis spongothorax radiolarian RADIOLARIANJ TAX,A
N)L IoQ?
Ica -Ju
j
iIll
LJ
L
L X IJJ
zones is correlated to the paleomagnetic time scal (figure 1). This datum falls within orjust after even "b" of the Gilbert reversed magnetic epoc] (t=4.14 to 3.90 million years before present and within the tentative Tau radiolarian zone pre viously suggested by Hays and Opdyke (1967) Chen (1975) estimated that this zonal boundar' corresponds to the Miocene/ Pliocene boundary a defined by Berggren (1973) (-5.0 million year before present—the epoch 5/Gilbert reversed mag netic boundary). Data presented herein il1ustrat that this zonal boundary is much younger that previously assumed. It does, however, approximatiI the Miocene/Pliocene boundary, but only as it ha: been defined in New Zealand (Kennett and Wat kins, 1974). The Helotholus vema/Theocalyptra bicornis songothorax zonal boundary coincides with a major fauna change throughout the southern ocean (Weaver, ir preparation) and is most likely related to the sig nificant regional warming detected by Weaver anc Ciesielski (1973, 1974) and by Ciesielski anc Weaver (1974), which occurred during the middk of the Gilbert magnetic epoch (several common!)
2
-,-qi
LL (D
CD <
I
I oJiLj
I cI I (/)1
I iI a 6
SD
-
Sig L3Q
E 38-8
LO
U U U
CL w
E34-5
0
140
0
loo
- I— Cr
Urn Z uJ _J 0
0 -
Cr
ju d a-
a
----°J !!'
U
4
0
RAID. ZONES
:n E 50-28
500
CONSISTENT OCCURRENCE TRACE
270
J?
El:
260
0 U Z UJ (1)
II
1. Figure Correlation of the Late Miocene-Early PIlocene radiolarian zones of Chen (1974, 1975) to the paleomagnetic time scale. Magnetic data for E34-5 th (57°23'S. 159°59'E.) is from Kennett and Brunner (1973); E38-8 (61°48'S. 149054'E.) is from Watkins and Kennett (1972); E5028 (62°54'S. 150'41'E.) was provided by N. D. Watkins, QL University of Rhode Island. Diatom and silicoflagellate biostratigraphy of McCollum (1975) and Ciesielski (1975) was utilized to correJ late core sequences.
ANTARCTIC JOURNAL
temperature change in the antarctic seas. Geology, 2(10): 511515. Havs,J. D., and N. D. ()pdvke. 1967. Antarctic radiolaria, magnetic reversals, and climatic change. Science, 158: 1001. Kennett, j. P., and C. A. Brunner. 1973. Antarctic late Cenozoic glaciation: evidence for initiation of ice-rafting and inferred bottom water activity. Geological Societ of America Bid/elm,
84: 2043-2052.
Kennett, J . P., and N. D. Watkins. 1974. Late Miocene-Early P1i icc ne paleomagnetic stratigraphy, paleoclimat )logy, and hiostratigraphy in New Zealand. Geological Society of America
Bulletin, 85: 1385-1398.
\lc( olium, D. W. 1975. Diatom stratigraphy of the southern ocean. In: Initial Reports of the Deep Sea Drilling Project, 28: 515-571. Washington, D.C., U.S. Government Printing Oflice. ()pdyke, N. D. 1972. Paleomagnetism of deep-sea cores. Re-
viewS of Geophysics and Space Physics, 10(1): 213-249.
Watkins, N. D., and .J P. Kennett. 1972. Regional sedimentary disconforities m and tipper Cenozoic changes in bottom water velocities between Australasia and Antarctica. Antarctic Re-
o(lrch Series, 19: 273-293.
Weaver, F. M. In preparation. Antarctic radiolaria from the southeast Pacific basin, Deep Sea Drilling Project. leg 35. Weaver, F. M., and P. F. Ciesielski. 1973. Pliocene plaeocliiiatic history recorded in antarctic deep-sea cores. Geological Societ y of America Annual Meeting. Abstracts with programs.
856-857.
Veavcr, F. M., anti P. F. Ciesielski. 1974. Pliocene paleotempetatures and regional correlation, southern ocean. Antarctic
Journal
of
the U.S.. 1X(5): 251-253.
Figure 2. (1) Dendrospyris haysi. (2) Triceraspyris coronatus.
(3) Theocalyptra bicornis spongothorax. (4) Prunopyle hayesi (interior view). (5) Lithomelissa sp. c. (6) Stylatractus universus (Pliocene form). For taxonomic details, see Chen (1974, 1975) and Weaver (in preparation.)
occurring radiolarian species that become extinct at this time are illustrated in figure 2). A more detailed discussion of data presented here will be included in the Initial Reports of the Deep Sea Drilling Project, Leg 35. This research was supported by a Penrose grant from the Geological Society of America, and by National Science Foundation grant OPP 74-20109. References
Berggren, W. A. 1973. The Pliocene time scale: calibration of planktonic foraminifera and calcareous nanoplankton zones.
Nature, 243: 391-397.
Chen, P. H. 1974. Some new Tertiary radiolarians from antarctic deep-sea sediments. Micropaleontology, 20(4): 480-492. Chen, P. H. 1975. Antarctic radiolarians. In: Initial Reports of the Deep Sea Drilling Project, 28: 437-513. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F. 1975. Biostratigraphy and paleoecology of Neogene and Oligocene silicofiagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project, 28: 625-692. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F., and F. M. Weaver. 1974. Early Pliocene
September/October 1975
Oligocene unconformity in southeast Indian Ocean piston cores MELVIN J . MIYAJIMA
Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306 During Deep Sea Drilling Project (DSDP) legs 21, 26, and 29, a regional unconformity of EoceneOligocene age was noted in the southwest Pacific and south Indian oceans. The unconformity was observed as sediment disconformities or as dissolution facies barren of calcareous microfossils (Luyendyk and Davies, 1974). Examination of four USNS Eltanin piston cores (table) indicates a similar unconformity dated between late Eocene and early Oligocene age. Distinct lithologic changes across the unconformities were observed in all cores. Cores E45-16, E45-19, and E48-49, located in a basin southeast 271
