Antarctic Peninsula and South Shetland Islands
Character of modern glacial marine sediments: Antarctic Peninsula and South Shetland Islands
which include water depth, distance from source (for example the glacier terminus), ice drainage area, and bay geometry. Water-column studies are also being conducted to understand better the mechanisms of sediment transport (Domack and Williams in press; Williams 1989; Williams, Boies, and Domack, Antarctic Journal, this issue). Textural analyses include the determination of gravel, sand, and mud ratios using standard wet-sieving techniques. Total organic carbon contents were determined using a LECO induction furnace and were corrected for calcium carbonate. The textural and total organic carbon measures provide a means to determine the relative contribution of biogenic (opaline silica) and terrigenous constituents, in that biogenic-rich sediments are less arenaceous and have higher total organic carbon (generally greater than 1 percent in modern antarctic sediments) (Domack et al. 1989; Dunbar et al. 1985; DeMaster et al. 1987). These parameters can be compared to water depths and distances from the ice front within individual bays to establish primary controls upon the terrigenous to biogenic facies transition (figure la, b). Sand contents show some degree of scatter for both distance and water depth, but the scatter is
A. BURKLEY, and
EUGENE W. DOMACK, LEWIS
CIIESLEY R. WILLIAMS
Depa rtnit'u t of Gr'oloi 1-lamilton Collr''e Clinton, New York 13323
Surface sediments were collected from bays and fjords along the Antarctic Peninsula during USAP-88 cruise III of the RIV Polar Duke (Domack 1988). Compositional and textural analyses of these sediments have been undertaken to define modern processes and the controls upon deposition. The exceptional sampling density allows for quantitative analyses of variables
Data from "usap88 surface seds."
Data from "usap88 surface seds."
2.0
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200 400 600
Data from "usap88 surface seds."
..
•t
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Water Depth (m)
80
on
I
Water Depth (m)
Data from "usap88 surface seds."
U U U U U - U U on Ra F m a U • U o n
rfg'
0
800
200 400 600
0
U U
1
12
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U
.c
0
MO 115
40-
1.5
5 10 15 20
Distance (km)
00 0 0 0 0 0 0 0 0 0 0 000 0 0 6) Ebo'08 coo 0 3cb00
0
0.00 5 10 15 20
B
Distance (km)
Figure 1. A. Scatter plot of sand content of ocean floor surface sediments vs. water depth and distance from the glacier terminus. Data are for bays and fjords along the Antarctic Peninsula and South Shetland Islands. Sample locations can be found in Domack (1988). B. Scatter plot of total organic carbon (TOC) (as weight percent in ocean floor surface sediments vs. water depth and distance from the glacier terminus. (km denotes kilometers.)
1989 REVIEW
113
USAP-88 Cierva Cove
40
1.8 1.4 1.2 1.0 0.8 0.6 0.4 0.2
30 20 10 0
0
MA
5 10 Distance (km)
USAP-88 Brialmont Cove
0.0
USAP88 Cierva Cove 0.020
0.016
0.016
0.012
•e 0.012 C
0.008 0 0.004
0.008 0.004
0
5 10 15 Distance (km)
0.000
20
USAP-88 Lapeyrere Bay
5 10 15 20 Distance (km)
100
80
80
60
S
60 -CS
40
20 0
0
USAP-88 Lester Cove
100
-C S
5 10 15 Distance (km)
0
0.020
0.000
USAP-88 Cierva Cove
40 S..
20 U
ii) ID
Distance (km)
0
S • .
$
0 5 10 15 Distance (km)
Figure 2. A. Down fjord decrease in sand content and increase in total organic carbon for surface sediments in Cierva Cove. (For sample locations see Domack 1988.) B. Organic richness of mud fraction (percent total organic carbon/percent mud) vs. distance from the ice front in Cierva Cove and Brialmont Cove. (For sample locations see Domack 1988.) C. Down fjord decrease in sand contents vs. distance from the ice front in Lapeyere Bay and Andvord Bay. (m denotes meters. km denotes kilometers.)
114
ANTARCTIC JOURNAL
noticeably less for the distance plot. This indicates that proximity to the ice front (primary sediment source) is more important in controlling sediment texture than the water depth is. A similar comparison can be observed for the total organic carbon, except that the scatter for the distance plot is even less pronounced. All plots show the general trend of decreasing sand content and increasing total organic carbon with increasing distance from the ice front and increasing water depths. The scatter plots in figure 1 are actually composed of a series of well-ordered linear and exponential relationships as defined by samples within individual bays and fjords. Several such plots are shown in figure 2a-c. For example, figure 2a shows samples obtained along the central axis of Cierva Cove, a fjord located along the northern end of the Danco Coast (64°05'S 61°W). The data clearly show that distance from the ice front controls the composition and texture of fjord basin sediments; water depth is secondary in its influence. The situation is somewhat more complex if samples are included from the fjord sidewalls and outer sills (Williams 1989). The utility of the data set shown in figure 2a is that temporal variations in ice-front positions or transport mechanisms can be determined from analyses of core samples. This work is currently being undertaken at Hamilton College for over 25 sediment cores which were collected from various basins along the Peninsula (Domack 1988). Additional data shown in figure 2b demonstrate the influence of ice drainage basin size on terrigenous sediment supply to fjord systems. One way of measuring the terrigenous sediment supply to the system is to determine the organic richness of the mud fraction; as given by the ratio of total organic carbon and mud percentages. Those systems receiving significant amounts of "meltwater" will have lower ratios since glacial derived silt will dilute the organic carbon fraction. The plot in figure 2b shows data from Cierva and Brialmont Cove. The two trends of similar slope with differing "Y intercepts" indicate that the samples from Brialmont Cove contain more terrigenous fines, at a given distance from the sediment source, than the samples from Cierva Cove. Though this difference could be due to a number of factors, the most obvious seems to be the size of the ice drainage basin, which is some 382 square kilometers for Cierva Cove and some 820 square kilometers (minimum estimate) for Brialmont Cove (Williams et
1989 REVIEW
al., Antarctic Journal, this issue). Both coves have identical climatic regimes, similar ice-surface slopes, aspect, and geometry. Bay geometry is another important variable; it influences the facies transitions quite dramatically. For instance, linear fjord systems like Lapeyrere Bay are marked by well-defined facies transitions with distance from the fjord head glacier (figure 2c). In contrast, large, open embayments such as Andvord Bay have more complex lateral and longitudinal facies changes (figures 2c). This is because multiple sediment sources begin to play a role in these bay systems and Coriolis forces also begin to influence the transport path of suspended material in the water column (Domack and Williams in press). This work was funded by National Science Foundation DPP grant 86-13565 to Hamilton College. We would also like to thank the American Chemical Society, Petroleum Research Fund for their support. References DeMaster, D.J., T.M. Nelson, C.A. Nittrouer, and S.L. Harden. 1987. Biogenic silica and organic carbon accumulation in modern Bransfield Straight sediments. Antarctic Journal of the U.S., 22, 108-110. Domack, E.W., and C.R. Williams. in press. Fine structureand suspended sedinien t transport in three A ii ta rctic Fjords. (Antarctic Research Series, First Annual Volume.) Washington, D.C.: American Geophysical Union. Domack, E.W., A.T.J. Jull, J.B. Anderson, T.W. Linick, and C.R. Williams. 1989. Application of tandem accelarator mass-spectrometer dating to Late Pleistocene-Holocene sediments of the East Antarctic continental shelf. Quaternary Research, 31, 277-287. Domack, E.W. 1988. Depositional environments of the Antarctic continental shelf: Fjord studies from the RIV Polar Duke. Antarctic Journal of the U. S., 23(5), 96-102. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. 1985. Oceanographic influences on sedimentation along the Antarctic continental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Continental Shelf. (Antarctic Research Series, Vol. 43.) Washington, D.C.: American Geophysical Union. Williams, C., C. Boies, and E.W. Domack. 1989. Glacial Drainage systems along the Antarctic Peninsula and Palmer Archipelago. Antarctic Journal of the U.S., 24(5). Williams, C.R. 1989. Temperature and sediment characteristics of a polar fjord: Cierva Cove, Antarctica. (B.A.
Thesis, Hamilton College, Clinton, New York.)
115
which include water depth, distance from source (for example the glacier terminus), ice drainage area, and bay geometry. Water-column studies are also being conducted to understand better the mechanisms of sediment transport (Domack and Williams in press; Williams 1989; Williams, Boies, and Domack, Antarctic Journal, this issue). Textural analyses include the determination of gravel, sand, and mud ratios using standard wet-sieving techniques. Total organic carbon contents were determined using a LECO induction furnace and were corrected for calcium carbonate. The textural and total organic carbon measures provide a means to determine the relative contribution of biogenic (opaline silica) and terrigenous constituents, in that biogenic-rich sediments are less arenaceous and have higher total organic carbon (generally greater than 1 percent in modern antarctic sediments) (Domack et al. 1989; Dunbar et al. 1985; DeMaster et al. 1987). These parameters can be compared to water depths and distances from the ice front within individual bays to establish primary controls upon the terrigenous to biogenic facies transition (figure la, b). Sand contents show some degree of scatter for both distance and water depth, but the scatter is
A. BURKLEY, and
EUGENE W. DOMACK, LEWIS
CIIESLEY R. WILLIAMS
Depa rtnit'u t of Gr'oloi 1-lamilton Collr''e Clinton, New York 13323
Surface sediments were collected from bays and fjords along the Antarctic Peninsula during USAP-88 cruise III of the RIV Polar Duke (Domack 1988). Compositional and textural analyses of these sediments have been undertaken to define modern processes and the controls upon deposition. The exceptional sampling density allows for quantitative analyses of variables
Data from "usap88 surface seds."
Data from "usap88 surface seds."
2.0
100 0
D
0
80 -
if
9 0
60-
I..
0 o
EP
0
E 55
20-
M
13
0
DEll
1.0•
C
°
EP]
0.5-
B
0
j
Bc
0.0-
-
U
100
60 40 20
0
V. • .
1.5
•.I S.
.
1.0 C
.
• •.
0.5
S .
0
800
2.0
e
-C
I
200 400 600
Data from "usap88 surface seds."
..
•t
U
Water Depth (m)
80
on
I
Water Depth (m)
Data from "usap88 surface seds."
U U U U U - U U on Ra F m a U • U o n
rfg'
0
800
200 400 600
0
U U
1
12
30 0 0 an B
U
.c
0
MO 115
40-
1.5
5 10 15 20
Distance (km)
00 0 0 0 0 0 0 0 0 0 0 000 0 0 6) Ebo'08 coo 0 3cb00
0
0.00 5 10 15 20
B
Distance (km)
Figure 1. A. Scatter plot of sand content of ocean floor surface sediments vs. water depth and distance from the glacier terminus. Data are for bays and fjords along the Antarctic Peninsula and South Shetland Islands. Sample locations can be found in Domack (1988). B. Scatter plot of total organic carbon (TOC) (as weight percent in ocean floor surface sediments vs. water depth and distance from the glacier terminus. (km denotes kilometers.)
1989 REVIEW
113
USAP-88 Cierva Cove
40
1.8 1.4 1.2 1.0 0.8 0.6 0.4 0.2
30 20 10 0
0
MA
5 10 Distance (km)
USAP-88 Brialmont Cove
0.0
USAP88 Cierva Cove 0.020
0.016
0.016
0.012
•e 0.012 C
0.008 0 0.004
0.008 0.004
0
5 10 15 Distance (km)
0.000
20
USAP-88 Lapeyrere Bay
5 10 15 20 Distance (km)
100
80
80
60
S
60 -CS
40
20 0
0
USAP-88 Lester Cove
100
-C S
5 10 15 Distance (km)
0
0.020
0.000
USAP-88 Cierva Cove
40 S..
20 U
ii) ID
Distance (km)
0
S • .
$
0 5 10 15 Distance (km)
Figure 2. A. Down fjord decrease in sand content and increase in total organic carbon for surface sediments in Cierva Cove. (For sample locations see Domack 1988.) B. Organic richness of mud fraction (percent total organic carbon/percent mud) vs. distance from the ice front in Cierva Cove and Brialmont Cove. (For sample locations see Domack 1988.) C. Down fjord decrease in sand contents vs. distance from the ice front in Lapeyere Bay and Andvord Bay. (m denotes meters. km denotes kilometers.)
114
ANTARCTIC JOURNAL
noticeably less for the distance plot. This indicates that proximity to the ice front (primary sediment source) is more important in controlling sediment texture than the water depth is. A similar comparison can be observed for the total organic carbon, except that the scatter for the distance plot is even less pronounced. All plots show the general trend of decreasing sand content and increasing total organic carbon with increasing distance from the ice front and increasing water depths. The scatter plots in figure 1 are actually composed of a series of well-ordered linear and exponential relationships as defined by samples within individual bays and fjords. Several such plots are shown in figure 2a-c. For example, figure 2a shows samples obtained along the central axis of Cierva Cove, a fjord located along the northern end of the Danco Coast (64°05'S 61°W). The data clearly show that distance from the ice front controls the composition and texture of fjord basin sediments; water depth is secondary in its influence. The situation is somewhat more complex if samples are included from the fjord sidewalls and outer sills (Williams 1989). The utility of the data set shown in figure 2a is that temporal variations in ice-front positions or transport mechanisms can be determined from analyses of core samples. This work is currently being undertaken at Hamilton College for over 25 sediment cores which were collected from various basins along the Peninsula (Domack 1988). Additional data shown in figure 2b demonstrate the influence of ice drainage basin size on terrigenous sediment supply to fjord systems. One way of measuring the terrigenous sediment supply to the system is to determine the organic richness of the mud fraction; as given by the ratio of total organic carbon and mud percentages. Those systems receiving significant amounts of "meltwater" will have lower ratios since glacial derived silt will dilute the organic carbon fraction. The plot in figure 2b shows data from Cierva and Brialmont Cove. The two trends of similar slope with differing "Y intercepts" indicate that the samples from Brialmont Cove contain more terrigenous fines, at a given distance from the sediment source, than the samples from Cierva Cove. Though this difference could be due to a number of factors, the most obvious seems to be the size of the ice drainage basin, which is some 382 square kilometers for Cierva Cove and some 820 square kilometers (minimum estimate) for Brialmont Cove (Williams et
1989 REVIEW
al., Antarctic Journal, this issue). Both coves have identical climatic regimes, similar ice-surface slopes, aspect, and geometry. Bay geometry is another important variable; it influences the facies transitions quite dramatically. For instance, linear fjord systems like Lapeyrere Bay are marked by well-defined facies transitions with distance from the fjord head glacier (figure 2c). In contrast, large, open embayments such as Andvord Bay have more complex lateral and longitudinal facies changes (figures 2c). This is because multiple sediment sources begin to play a role in these bay systems and Coriolis forces also begin to influence the transport path of suspended material in the water column (Domack and Williams in press). This work was funded by National Science Foundation DPP grant 86-13565 to Hamilton College. We would also like to thank the American Chemical Society, Petroleum Research Fund for their support. References DeMaster, D.J., T.M. Nelson, C.A. Nittrouer, and S.L. Harden. 1987. Biogenic silica and organic carbon accumulation in modern Bransfield Straight sediments. Antarctic Journal of the U.S., 22, 108-110. Domack, E.W., and C.R. Williams. in press. Fine structureand suspended sedinien t transport in three A ii ta rctic Fjords. (Antarctic Research Series, First Annual Volume.) Washington, D.C.: American Geophysical Union. Domack, E.W., A.T.J. Jull, J.B. Anderson, T.W. Linick, and C.R. Williams. 1989. Application of tandem accelarator mass-spectrometer dating to Late Pleistocene-Holocene sediments of the East Antarctic continental shelf. Quaternary Research, 31, 277-287. Domack, E.W. 1988. Depositional environments of the Antarctic continental shelf: Fjord studies from the RIV Polar Duke. Antarctic Journal of the U. S., 23(5), 96-102. Dunbar, R.B., J.B. Anderson, E.W. Domack, and S.S. Jacobs. 1985. Oceanographic influences on sedimentation along the Antarctic continental shelf. In S.S. Jacobs (Ed.), Oceanology of the Antarctic Continental Shelf. (Antarctic Research Series, Vol. 43.) Washington, D.C.: American Geophysical Union. Williams, C., C. Boies, and E.W. Domack. 1989. Glacial Drainage systems along the Antarctic Peninsula and Palmer Archipelago. Antarctic Journal of the U.S., 24(5). Williams, C.R. 1989. Temperature and sediment characteristics of a polar fjord: Cierva Cove, Antarctica. (B.A.
Thesis, Hamilton College, Clinton, New York.)
115
