Basal sediment ages of ARA Islas Orcadas cruise 12 piston cores
McCollum, D. W. 1975. Antarctic Cenozoic diatoms: Leg 28, Deep Sea Drilling Project. In: Initial reports of the Deep Sea Drilling Project, 28 (L. A. Frakes, et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 515-572. Sclater,J. G., D. Woodroffe, H. Dick, D. Georgi, S. W. Wise,Jr., and P. Ciesielski. 1977. Islas Orcadas cruise 11, Buenos Aires to Cape Town. Antarctic Journal of the US., 12(4): 62-65. Weaver, F. M. 1976. Late Miocene and Pliocene radiolarian paleobiogeography and biostratzgraphy of the Southern Ocean. Unpublished doctoral dissertation, Department of Geology, Florida State University.
Basal sediment ages of ARA Islas Orcadas cruise 12 piston cores DAVID R. DEFELICE
Antarctic Marine Geology Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
Preliminary basal sediment ages for 39 of the 46 piston cores recovered on ARA Islas Orcadas cruise 12 (figure) are presented here to aid others working on southern-oceanoriented research. (Seven cores were found to be barren of microfossils diagnostic for age determination.) Cruise 12 began in Capetown, South Africa, in January 1977 and ended in March 1977 in Buenos Aires, Argentina. The objectives of the coring operation were to improve core control in the southeast sector of the South Atlantic Ocean as a means of increasing understanding of the depositional history of the area. Most cores were taken in conjunction with physical oceanographic stations along geophysical seismic tracts, allowing for the integration of sedimentologic, hydrologic, and structural data. The table lists piston core number, latitude, longitude, water depth, sample interval, core length, and basal age. Sampling. Samples were taken within 6 centimeters of the base in 44 of the 46 piston cores (recovery in core 38 was limited to mud at the base of the piston; only core catcher sediment was retrieved from core 45). Samples were also taken from core catcher and/or cutter (c/c) sediment wherever possible. Cores having disturbed bases were sampled at the base of the undisturbed section as well. In all but one core (core 18), biostratigraphic examination of samples from the c/c, core base, and the base of the undisturbed section has yielded similar ages. Cores that were found to be barren at the base were sampled and examined whenever possible at 20-centimeter intervals farther up the core until microfossils, diagnostic for
October 1978
age determination, were found. For these cores (1, 20, 24), the ages given in the table may not be basal ages and are given only to offer rough estimates of sedimentation rate. These cores are labeled in the table. Laboratory. Smear slides were made of the sampled material and were examined for their diatom, silicoflagellate, and calcareous nannofossil content. The intervals were then age-dated using the biostratigraphic zonations defined by McCollum (1975) for diatoms, and Weaver's (1976) modification of McCollum's zonation was used whenever possible for the early Pliocene; Ciesielski (1975) for silicoflagellates; and Wise and Wind (1977) for calcareous nannofossils. Because description and thorough biostratigraphic examination of each core had not been completed at the time of preparation of this article, these basal age dates must be considered preliminary. For many cores, age dates were determined on the basis of only one or two samples. It is difficult without further, more thorough examination of the cores to realize fully the extent of reworking and contamination factors that would lead to improper age assignments. Many samples taken from the southernmost cores of cruise 12 indicate the occurrence of intense reworking, possibly due to turbidite deposition in the southern Weddell Basin. I appreciate the assistance of Dennis Cassidy, Alan Brown, and Rosemary Raymond in the preparation of this article. Research was done under National Science Foundation grant DPP 77-19360.
Core location map for Islas Orcadas cruise 1277.
97
Piston Core Number
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 3B 39B 40 41 42 43 44 45 46 *
Latitude(S) 39'31 .8' 45'02 1 46'59. 7• 47*59 3 49*01.0 49'299' 49* 59. 50'32. 5' 51*00.8 52'Ol .1 53'OOO' 54'OO 6' 56' 16. 0' 58'26.5' 59'315' 61'Ol.8' 61' 59. 3' 63'OO.l'
Longitude
Water Depth (m)
16*51 .5'E 22 28. 2' E 21* 55. SE 21'34.9'E 21'21.2'E 21'10.6E 21*06.9 20053.0'E 20*44.3 20028.3'E 20* 05 . 6' E l9'47. SE 19004.2'E 18*14.9 17*50.6 E 17'26.7'E 16*57.7E 16*37.1 'E
4806 4806 5055 4559 4610 4243 4153 4492 4151 2740 3027 3178 4100 4682 5066 4921 4988 5022
16*11 .2'E 15'44.6'E 1S'20.4'E 14'52.4'E 14'34.8'E 11'58.8'E 10057.9'E 09'll.O'E 09'07.7'E 90'll.O'E 09'00.3'E 06007.4'E 04*09.5 E 03* 06 . 0' E 02*28.7 E 0l'33.3'E 0l'46.7'E 00027.9'E 00'40. SW 01*50.1W 03*05.7W 04019.7'W 05'04.6'W 15*00.7W 23'58.9W 18*31 .6'W 22041.2'W 28*38.3W
4949 3886 3603 3904 3698 1862 2015 4658 4846 5322 4976 5229 5240 5227 4184 2679 2527 3440 4473 4444 4062 2970 1873 4918 4724 4910 4786 4563
0
63'59. 7' 65'OO.l' 66'00.8' 67'Ol .2' 67 o 53. 8 ' 68'lO.O' 68036.51 65'01.6' 62o56.01 61 28. 0' 59'314' 60'Ol .2' 62'Ol .6' 53'00.4' 63 33. 5' 64028.81 64 27. 3' 65032.11 66 30. 5' 67' 29 . 4' 68'29.8' 69' 29 . 6' 69'599' 66' 00 . 3' 68'19.8' 65' 30. 2' 67'26.3' 68' 49 . 5'
0
0 0 0
Sample Interval (cm) 79*; 676 1136 C/C 416; C/C 39;C/C 519; 588; C/C 919;1208;C/C 1059;1193;C/C 1 183;C/C 11 75;C/C 1178 ; C/C l678;C/C 377 ; 983 ; C/C 1019;1167;C/C 821 ;1062;C/C 983;C/C 30;1721 ;C/C 1491 ;1800;C/C 1701 ;C/C 42 l670;C/C 1038; 1673 ;C/C 461*, 891, 1303, C/C 990,1171 ;C/C 1193;C/C 43; 950 ; C/C 459*; 5 59; 1179 ; C/C 841 ;1171;C/C 1081 ;1731 ;C/C 1803;C/C 205; C/C 579;1204;C/C 1 730;C/C 1731 ;1790;C/C 1439;1749;C/C 9;1649;C/C 488;1220;C/C llg;1730 495;1343 1273 Mud at Base of Piston 286 ; C/C 1220; C/C 259;1171 334;C/C 110 ; C/C 501 ;C/C C/C 553;C/C
Core Length(cm) 1137 417 43 590 1212 1194 1187 1178 1179 1680 985 1168 1063 984 1723 1801 1705 1671 1674 1304 1172 1194 951 1180 1172 1732 1804 206 1205 1733 1791 1750 1650 1221** 1736** 1344 1274 288 l221** 1173 337 112 502** C/C only 556
Age Late Pliocene Late Pliocene Late Pliocene Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Early Pliocene Paleocene (nanno Ooze) Late Miocene Early Pliocene Early Pliocene (reworked Miocene) Late Pliocene Early liocene(reworked Miocene) Early Pliocene (reworked Miocene) Middle Miocene? Late Miocene Early Pliocene BARREN Quaternary Middle Miocene Late Miocene Early Pliocene (reworked Miocene) Quaternary BARREN Early Pliocene reworked Miocen Early Pliocene reworked Miocen Early Pliocene reworked Miocen Late Miocene (probably reworked) Early Pliocene Early Pliocene Middle Miocene Early Pliocene (reworked Miocene) Quaternary Quaternary Quaternary Quaternary BARREN BARREN BARREN BARREN BARREN
P
Core date based on this interval. All intervals below this interval were found to be barren of microfossils diagnostic for age determination. Ages assigned may not be basal ages.
** Undescribed Core lengths.
Basal sediment ages of piston cores. References
Ciesielski, P. F. 1975. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project, 28 (L. A. Frakes et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 625-691. McCollum, D. W. 1975. Antarctic Cenozoic diatoms: Leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Proj-
98
ect, 28 (L. A. Frakes et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 515-572. Weaver, F. M. 1976. Late Miocene and Pliocene radiolarian paleobiogeography and biostratigraphy of the southern ocean. Unpublished doctoral dissertation, Department of Geology, Florida State University, Tallahassee, Florida. Wise, S. W., Jr., and F. H. Wind. 1977. Mesozoic and Cenozoic calcareous nannofossils recovered by D.S.D.P. leg 36 drilling on the Falkland Plateau, Atlantic sector of the southern ocean. In: Initial Reports of the Deep Sea Drilling Project, 36 (P. F. Barker et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 269-492.
ANTARCTIC JOURNAL
Basal sediment ages of ARA Islas Orcadas cruise 12 piston cores DAVID R. DEFELICE
Antarctic Marine Geology Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
Preliminary basal sediment ages for 39 of the 46 piston cores recovered on ARA Islas Orcadas cruise 12 (figure) are presented here to aid others working on southern-oceanoriented research. (Seven cores were found to be barren of microfossils diagnostic for age determination.) Cruise 12 began in Capetown, South Africa, in January 1977 and ended in March 1977 in Buenos Aires, Argentina. The objectives of the coring operation were to improve core control in the southeast sector of the South Atlantic Ocean as a means of increasing understanding of the depositional history of the area. Most cores were taken in conjunction with physical oceanographic stations along geophysical seismic tracts, allowing for the integration of sedimentologic, hydrologic, and structural data. The table lists piston core number, latitude, longitude, water depth, sample interval, core length, and basal age. Sampling. Samples were taken within 6 centimeters of the base in 44 of the 46 piston cores (recovery in core 38 was limited to mud at the base of the piston; only core catcher sediment was retrieved from core 45). Samples were also taken from core catcher and/or cutter (c/c) sediment wherever possible. Cores having disturbed bases were sampled at the base of the undisturbed section as well. In all but one core (core 18), biostratigraphic examination of samples from the c/c, core base, and the base of the undisturbed section has yielded similar ages. Cores that were found to be barren at the base were sampled and examined whenever possible at 20-centimeter intervals farther up the core until microfossils, diagnostic for
October 1978
age determination, were found. For these cores (1, 20, 24), the ages given in the table may not be basal ages and are given only to offer rough estimates of sedimentation rate. These cores are labeled in the table. Laboratory. Smear slides were made of the sampled material and were examined for their diatom, silicoflagellate, and calcareous nannofossil content. The intervals were then age-dated using the biostratigraphic zonations defined by McCollum (1975) for diatoms, and Weaver's (1976) modification of McCollum's zonation was used whenever possible for the early Pliocene; Ciesielski (1975) for silicoflagellates; and Wise and Wind (1977) for calcareous nannofossils. Because description and thorough biostratigraphic examination of each core had not been completed at the time of preparation of this article, these basal age dates must be considered preliminary. For many cores, age dates were determined on the basis of only one or two samples. It is difficult without further, more thorough examination of the cores to realize fully the extent of reworking and contamination factors that would lead to improper age assignments. Many samples taken from the southernmost cores of cruise 12 indicate the occurrence of intense reworking, possibly due to turbidite deposition in the southern Weddell Basin. I appreciate the assistance of Dennis Cassidy, Alan Brown, and Rosemary Raymond in the preparation of this article. Research was done under National Science Foundation grant DPP 77-19360.
Core location map for Islas Orcadas cruise 1277.
97
Piston Core Number
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 3B 39B 40 41 42 43 44 45 46 *
Latitude(S) 39'31 .8' 45'02 1 46'59. 7• 47*59 3 49*01.0 49'299' 49* 59. 50'32. 5' 51*00.8 52'Ol .1 53'OOO' 54'OO 6' 56' 16. 0' 58'26.5' 59'315' 61'Ol.8' 61' 59. 3' 63'OO.l'
Longitude
Water Depth (m)
16*51 .5'E 22 28. 2' E 21* 55. SE 21'34.9'E 21'21.2'E 21'10.6E 21*06.9 20053.0'E 20*44.3 20028.3'E 20* 05 . 6' E l9'47. SE 19004.2'E 18*14.9 17*50.6 E 17'26.7'E 16*57.7E 16*37.1 'E
4806 4806 5055 4559 4610 4243 4153 4492 4151 2740 3027 3178 4100 4682 5066 4921 4988 5022
16*11 .2'E 15'44.6'E 1S'20.4'E 14'52.4'E 14'34.8'E 11'58.8'E 10057.9'E 09'll.O'E 09'07.7'E 90'll.O'E 09'00.3'E 06007.4'E 04*09.5 E 03* 06 . 0' E 02*28.7 E 0l'33.3'E 0l'46.7'E 00027.9'E 00'40. SW 01*50.1W 03*05.7W 04019.7'W 05'04.6'W 15*00.7W 23'58.9W 18*31 .6'W 22041.2'W 28*38.3W
4949 3886 3603 3904 3698 1862 2015 4658 4846 5322 4976 5229 5240 5227 4184 2679 2527 3440 4473 4444 4062 2970 1873 4918 4724 4910 4786 4563
0
63'59. 7' 65'OO.l' 66'00.8' 67'Ol .2' 67 o 53. 8 ' 68'lO.O' 68036.51 65'01.6' 62o56.01 61 28. 0' 59'314' 60'Ol .2' 62'Ol .6' 53'00.4' 63 33. 5' 64028.81 64 27. 3' 65032.11 66 30. 5' 67' 29 . 4' 68'29.8' 69' 29 . 6' 69'599' 66' 00 . 3' 68'19.8' 65' 30. 2' 67'26.3' 68' 49 . 5'
0
0 0 0
Sample Interval (cm) 79*; 676 1136 C/C 416; C/C 39;C/C 519; 588; C/C 919;1208;C/C 1059;1193;C/C 1 183;C/C 11 75;C/C 1178 ; C/C l678;C/C 377 ; 983 ; C/C 1019;1167;C/C 821 ;1062;C/C 983;C/C 30;1721 ;C/C 1491 ;1800;C/C 1701 ;C/C 42 l670;C/C 1038; 1673 ;C/C 461*, 891, 1303, C/C 990,1171 ;C/C 1193;C/C 43; 950 ; C/C 459*; 5 59; 1179 ; C/C 841 ;1171;C/C 1081 ;1731 ;C/C 1803;C/C 205; C/C 579;1204;C/C 1 730;C/C 1731 ;1790;C/C 1439;1749;C/C 9;1649;C/C 488;1220;C/C llg;1730 495;1343 1273 Mud at Base of Piston 286 ; C/C 1220; C/C 259;1171 334;C/C 110 ; C/C 501 ;C/C C/C 553;C/C
Core Length(cm) 1137 417 43 590 1212 1194 1187 1178 1179 1680 985 1168 1063 984 1723 1801 1705 1671 1674 1304 1172 1194 951 1180 1172 1732 1804 206 1205 1733 1791 1750 1650 1221** 1736** 1344 1274 288 l221** 1173 337 112 502** C/C only 556
Age Late Pliocene Late Pliocene Late Pliocene Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Quaternary Early Pliocene Paleocene (nanno Ooze) Late Miocene Early Pliocene Early Pliocene (reworked Miocene) Late Pliocene Early liocene(reworked Miocene) Early Pliocene (reworked Miocene) Middle Miocene? Late Miocene Early Pliocene BARREN Quaternary Middle Miocene Late Miocene Early Pliocene (reworked Miocene) Quaternary BARREN Early Pliocene reworked Miocen Early Pliocene reworked Miocen Early Pliocene reworked Miocen Late Miocene (probably reworked) Early Pliocene Early Pliocene Middle Miocene Early Pliocene (reworked Miocene) Quaternary Quaternary Quaternary Quaternary BARREN BARREN BARREN BARREN BARREN
P
Core date based on this interval. All intervals below this interval were found to be barren of microfossils diagnostic for age determination. Ages assigned may not be basal ages.
** Undescribed Core lengths.
Basal sediment ages of piston cores. References
Ciesielski, P. F. 1975. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project, 28 (L. A. Frakes et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 625-691. McCollum, D. W. 1975. Antarctic Cenozoic diatoms: Leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Proj-
98
ect, 28 (L. A. Frakes et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 515-572. Weaver, F. M. 1976. Late Miocene and Pliocene radiolarian paleobiogeography and biostratigraphy of the southern ocean. Unpublished doctoral dissertation, Department of Geology, Florida State University, Tallahassee, Florida. Wise, S. W., Jr., and F. H. Wind. 1977. Mesozoic and Cenozoic calcareous nannofossils recovered by D.S.D.P. leg 36 drilling on the Falkland Plateau, Atlantic sector of the southern ocean. In: Initial Reports of the Deep Sea Drilling Project, 36 (P. F. Barker et al., eds.). U.S. Government Printing Office, Washington, D.C. pp. 269-492.
ANTARCTIC JOURNAL
