Basal sediment ages of 1983 piston cores
Basal sediment ages of 1983 piston cores F.A. KAHAROEDDIN and D.S. CASSIDY Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306
Presented here are the preliminary basal sediment ages (see table) of piston cores and bagged piston-core sediments recovered by 21 coring attempts during austral summer 1982 1983 in the Ross Sea/Sulzberger Bay area (figure) aboard the U.S. Coast Guard icebreaker Glacier. Most sediments recovered on this cruise are clastic glaciomarine sediments, as can be expected because of their proximity to the antarctic continent, and the sediments are either barren or contain very few microfossils. [For a summary of the scientific objectives and preliminary results of the 1983 antarctic piston-coring and grab-sampling program, see Anderson (1983). Detailed lithologic descriptions and other data attendant to the 1983 antarctic materials are presented by Kaharoeddin et al. (1984).1 The only significant presence of a biogenic component in any of these cores is found in core 17. That component consists of diatomaceous ooze and muddy diatomaceous ooze with diatoms that are moderately to poorly preserved. The age of this core is Late Miocene/Early Pliocene. 160'W
155'W
Icr,'w 5'S
6'S
The only common microfossils present in the glaciomarine sediments are diatoms; thus, the age-diagnostic diatoms were used in determining the basal sediment ages. The presence of reworked microfossils, commonly encountered in these sediments, made age determinations difficult. From the liner-encased cores, samples for analysis were taken from the bottom, or very near the bottom, of the undisturbed part of the sediment. In cases where the basal sediments are sand or pebbly sand (cores 24, 25B, 35), samples were taken from the lowermost fine grain sediments in which microfossils are most likely to occur. Core 35 was also sampled near the bottom (47 to 48 centimeters) of the lowermost fine grain sedimentary unit. In core 17, the bottom 3 centimeters of sediment contain abundant sedimentary clasts which are difficult to distinguish from autochthonous sediment. Therefore, an additional sample was taken several centimeters above the base of this core where the sediment is free of these clasts. In the case of bagged samples representing the sole recovery of sediment by the piston-corer at the ship station (26, 29, 30, 39), samples for analysis were taken from the middle part of the bagged sediment "lump," where the sediment sample is least likely to have become contaminated. Two smear slides were prepared from each sample and were examined, independently, by two workers for their diatom content. These analyses indicate that two-thirds of the total number of samples are barren of microfossils and that five of the fossiliferous samples contain only trace amounts, or less than 1 percent, of diatoms. To obtain the maximum number of age-diagnostic microfossils (microfossils that are scarce in glaciomarine sediments) on which to base reliable age-dates, all fossiliferous samples were processed to concentrate the diatoms. Approximately 1 cubic centimeter of each sample was wet sieved through a 63 micrometer sieve screen to remove the sand fraction. The fine fraction was then diluted with water to 50 milliliters and allowed to settle for 8 minutes. The supernatant, which contained most of the clay fraction, was decanted and discarded. The remaining slurry was diluted to 50 milliliters, and then allowed to settle for 1 minute to remove most of the silt. The supernatant was decanted and then concentrated by centrifugation. The concentrate was used to prepare two strewn slides for each sample; these slides were analyzed for age-dating. The ages of the sediments are based on the diatom zonation schemes of Weaver and Gombos (1981), as revised by Ciesielski (1983). Funding in support of this work was provided by National Science Foundation contract C-1059.
7'S
References
160'W
155'W
150'W
8'S
Làcatlon map of cores and grab samples retrieved aboard the U.S. COast Guard icebreaker Glacierduring austral summer 1982-1983. Note: Stations 14 and 45, located in the Ross Sea (table) could not be shown on this map.
195 REVIEW
Anderson, J.B. 1983. Preliminary results of the 1983 piston-coring program. Antarctic Journal of the U.S., 18(5), 157 - 158. Ciesielski, P.F. 1983. The Neogene and Quaternary diatom biostratigraphy of subantarctic sediments, Deep Sea Drilling Project Leg 71. In W.J. Ludwig, V.A. Krasheninnikov et al. (Eds.), Initial reports of the Deep Sea Drilling Project, (Vol. 71). Washington, D.C.: U.S. Government Printing Office.
121
Kaharoeddin, F.A., S. Knüttel, G. E. Wiegand, T.H. Lang, R. S. Graves, Weaver, F.M., and A.M. Gombos. 1981. Southern high-latitude diatom C.L. Humphreys, and P.F. Ciesielski. 1984. LISCGC Glacier: Operations biostratigraphy. In J.E. Warme, R.G. Douglas, and E.L. Winterer Deep Freeze 1982 (northern Antarctic Peninsula) and 1983 (Ross Sea- (Eds.), The Deep Sea Drilling Project: A decade of progress, (Special pubSulzberger Bay area) sediment descriptions (Contribution 52). Tallahassee: lication No. 32). Tulsa, Oklahoma: Society of Economic Paleon Florida State University, Department of Geology, Sedimentology Re- tologists and Mineralogists. search Laboratory.
Sediment ages of the piston cores Water Core Sample Core Latitude depth length interval Sediment number (south) Longitude (in meters) (in centimeters) (in centimeters) lithology Age
14' 17 18 19 22
78°28.8' 77°43.1' 77°26.4' 77°19.2' 76°57.3'
164-08.6'(W) 159-45.5'(W) 159-04.2'(W) 158-42.0'(W) 157-06.8'(W)
23 24 25B 26 28
76°59.0' 76°55.0' 76°57.9' 76°57.9' 76°49.8'
156-36.6'(W) 155-34.6'(W) 155027.2'(W) 155036.3'(W) 152-30.6'(W)
29 30 31 32 33
76°43.5' 76°35.8' 76°35.8' 76°36.0' 7638.6'
152039.5'(W) 153-11.3'(W) 154-05.9'(W) 155-33.3'(W) 156-21.5'(W)
34 35 36 37 39 45C
76°42.7' 76°26.0' 76°24.0' 76021.5' 76°28.0' 76°51.2'
156-14.9'(W) 157052.0'(W) 157055.0'(W) 157046.7'(W) 157-52.0'(W) 175056.3'(E)
a b
601 229 376 770 530 393 216 778 1207 1024 933 643 713 373 787 677 549 808 1390 347 330
277 53 78 225 92
276-277 44-45;52-53 69-70;77-78 221-222 90-91
M DO; MDO Sit; Sit SM SM
Quaternary Late Miocene/Early Pliocene Barren Barren Barren
74 104 22 BAGd 270
64-65;71-72 95-96 10-11 BAG 267-268
M; M MS M M PbM
Quaternary Barren Barren Quaternary Barren
BAG BAG 36 42 85
BAG BAG 35-36 40-41 83-84
sit Site M M M
Barren Quaternary Barren Barren Barren
59 162 276 300 BAG 35
54-55 47-48;76-77 273-274 270-271 BAG 34-35
MS M; SM M M S MS
Barren Barren Barren Barren Quaternary Quaternary?
Piston core numbers correspond to the ship stations numbers. "DO" denotes diatomaceous mud; "PbM" denotes pebbly mud; "M" denotes mud; "S' denotes sand; "MDO" denotes muddy diatomaceous ooze; "SM" denotes sandy mud; "MS' denotes muddy sand; "Sit" denotes silt The recovery locations of station numbers 14 and 45 are not shown on figure because their positions were considerably west of the area covered by the map.
ci
"BAG" denotes bag sample Matrix sediment.
122
ANTARCTIC JOURNAL
Presented here are the preliminary basal sediment ages (see table) of piston cores and bagged piston-core sediments recovered by 21 coring attempts during austral summer 1982 1983 in the Ross Sea/Sulzberger Bay area (figure) aboard the U.S. Coast Guard icebreaker Glacier. Most sediments recovered on this cruise are clastic glaciomarine sediments, as can be expected because of their proximity to the antarctic continent, and the sediments are either barren or contain very few microfossils. [For a summary of the scientific objectives and preliminary results of the 1983 antarctic piston-coring and grab-sampling program, see Anderson (1983). Detailed lithologic descriptions and other data attendant to the 1983 antarctic materials are presented by Kaharoeddin et al. (1984).1 The only significant presence of a biogenic component in any of these cores is found in core 17. That component consists of diatomaceous ooze and muddy diatomaceous ooze with diatoms that are moderately to poorly preserved. The age of this core is Late Miocene/Early Pliocene. 160'W
155'W
Icr,'w 5'S
6'S
The only common microfossils present in the glaciomarine sediments are diatoms; thus, the age-diagnostic diatoms were used in determining the basal sediment ages. The presence of reworked microfossils, commonly encountered in these sediments, made age determinations difficult. From the liner-encased cores, samples for analysis were taken from the bottom, or very near the bottom, of the undisturbed part of the sediment. In cases where the basal sediments are sand or pebbly sand (cores 24, 25B, 35), samples were taken from the lowermost fine grain sediments in which microfossils are most likely to occur. Core 35 was also sampled near the bottom (47 to 48 centimeters) of the lowermost fine grain sedimentary unit. In core 17, the bottom 3 centimeters of sediment contain abundant sedimentary clasts which are difficult to distinguish from autochthonous sediment. Therefore, an additional sample was taken several centimeters above the base of this core where the sediment is free of these clasts. In the case of bagged samples representing the sole recovery of sediment by the piston-corer at the ship station (26, 29, 30, 39), samples for analysis were taken from the middle part of the bagged sediment "lump," where the sediment sample is least likely to have become contaminated. Two smear slides were prepared from each sample and were examined, independently, by two workers for their diatom content. These analyses indicate that two-thirds of the total number of samples are barren of microfossils and that five of the fossiliferous samples contain only trace amounts, or less than 1 percent, of diatoms. To obtain the maximum number of age-diagnostic microfossils (microfossils that are scarce in glaciomarine sediments) on which to base reliable age-dates, all fossiliferous samples were processed to concentrate the diatoms. Approximately 1 cubic centimeter of each sample was wet sieved through a 63 micrometer sieve screen to remove the sand fraction. The fine fraction was then diluted with water to 50 milliliters and allowed to settle for 8 minutes. The supernatant, which contained most of the clay fraction, was decanted and discarded. The remaining slurry was diluted to 50 milliliters, and then allowed to settle for 1 minute to remove most of the silt. The supernatant was decanted and then concentrated by centrifugation. The concentrate was used to prepare two strewn slides for each sample; these slides were analyzed for age-dating. The ages of the sediments are based on the diatom zonation schemes of Weaver and Gombos (1981), as revised by Ciesielski (1983). Funding in support of this work was provided by National Science Foundation contract C-1059.
7'S
References
160'W
155'W
150'W
8'S
Làcatlon map of cores and grab samples retrieved aboard the U.S. COast Guard icebreaker Glacierduring austral summer 1982-1983. Note: Stations 14 and 45, located in the Ross Sea (table) could not be shown on this map.
195 REVIEW
Anderson, J.B. 1983. Preliminary results of the 1983 piston-coring program. Antarctic Journal of the U.S., 18(5), 157 - 158. Ciesielski, P.F. 1983. The Neogene and Quaternary diatom biostratigraphy of subantarctic sediments, Deep Sea Drilling Project Leg 71. In W.J. Ludwig, V.A. Krasheninnikov et al. (Eds.), Initial reports of the Deep Sea Drilling Project, (Vol. 71). Washington, D.C.: U.S. Government Printing Office.
121
Kaharoeddin, F.A., S. Knüttel, G. E. Wiegand, T.H. Lang, R. S. Graves, Weaver, F.M., and A.M. Gombos. 1981. Southern high-latitude diatom C.L. Humphreys, and P.F. Ciesielski. 1984. LISCGC Glacier: Operations biostratigraphy. In J.E. Warme, R.G. Douglas, and E.L. Winterer Deep Freeze 1982 (northern Antarctic Peninsula) and 1983 (Ross Sea- (Eds.), The Deep Sea Drilling Project: A decade of progress, (Special pubSulzberger Bay area) sediment descriptions (Contribution 52). Tallahassee: lication No. 32). Tulsa, Oklahoma: Society of Economic Paleon Florida State University, Department of Geology, Sedimentology Re- tologists and Mineralogists. search Laboratory.
Sediment ages of the piston cores Water Core Sample Core Latitude depth length interval Sediment number (south) Longitude (in meters) (in centimeters) (in centimeters) lithology Age
14' 17 18 19 22
78°28.8' 77°43.1' 77°26.4' 77°19.2' 76°57.3'
164-08.6'(W) 159-45.5'(W) 159-04.2'(W) 158-42.0'(W) 157-06.8'(W)
23 24 25B 26 28
76°59.0' 76°55.0' 76°57.9' 76°57.9' 76°49.8'
156-36.6'(W) 155-34.6'(W) 155027.2'(W) 155036.3'(W) 152-30.6'(W)
29 30 31 32 33
76°43.5' 76°35.8' 76°35.8' 76°36.0' 7638.6'
152039.5'(W) 153-11.3'(W) 154-05.9'(W) 155-33.3'(W) 156-21.5'(W)
34 35 36 37 39 45C
76°42.7' 76°26.0' 76°24.0' 76021.5' 76°28.0' 76°51.2'
156-14.9'(W) 157052.0'(W) 157055.0'(W) 157046.7'(W) 157-52.0'(W) 175056.3'(E)
a b
601 229 376 770 530 393 216 778 1207 1024 933 643 713 373 787 677 549 808 1390 347 330
277 53 78 225 92
276-277 44-45;52-53 69-70;77-78 221-222 90-91
M DO; MDO Sit; Sit SM SM
Quaternary Late Miocene/Early Pliocene Barren Barren Barren
74 104 22 BAGd 270
64-65;71-72 95-96 10-11 BAG 267-268
M; M MS M M PbM
Quaternary Barren Barren Quaternary Barren
BAG BAG 36 42 85
BAG BAG 35-36 40-41 83-84
sit Site M M M
Barren Quaternary Barren Barren Barren
59 162 276 300 BAG 35
54-55 47-48;76-77 273-274 270-271 BAG 34-35
MS M; SM M M S MS
Barren Barren Barren Barren Quaternary Quaternary?
Piston core numbers correspond to the ship stations numbers. "DO" denotes diatomaceous mud; "PbM" denotes pebbly mud; "M" denotes mud; "S' denotes sand; "MDO" denotes muddy diatomaceous ooze; "SM" denotes sandy mud; "MS' denotes muddy sand; "Sit" denotes silt The recovery locations of station numbers 14 and 45 are not shown on figure because their positions were considerably west of the area covered by the map.
ci
"BAG" denotes bag sample Matrix sediment.
122
ANTARCTIC JOURNAL
