Field collection for apatite fission track analysis, Ellsworth Mountains
Hammer, W.R. 1990. Triassic terrestrial vertebrate faunas of Antarctica. In T.N. Taylor and E.L. Taylor (Eds.), Antarctic paleobiology. New York: Springer-Verlag. Hammer, W.R., J.W. Collinson, and W.J. Ryan, III. 1990. A new Triassic vertebrate fauna from Antarctica and its depositional setting. Antarctic Science, 2(2), 163-167. Hammer, W.R., W.J. Ryan, J.W. Tamplin, and S.L. DeFauw. 1986.
New vertebrates from the Fremouw formation (Triassic) Beardmore Glacier region, Antarctica. Antarctic Journal of the U.S., 21(5), 24-26. Seeley, H.G. 1894. Researches on the structure, organization and classification of the fossil Reptilia. Part IX, section 1: On the Therosuchia. Philosophical Transactions of the Royal Society of London, series B, 185, 987-1,018.
Field collection for apatite fission track analysis, Ellsworth Mountains
85°W
EDMUND STUMP and PAUL C. FITZGERALD
Department of Geology Arizona State University Tempe, Arizona 85287-1404
We collected rock samples for fission track analysis in the Ellsworth Mountains during the 1989-1990 austral summer to provide an understanding of the tectonic history of this crustal block. In broader terms, the study will attempt to relate the uplift history of the Ellsworth Mountains to the tectonic evolution of West Antarctica. Because the put-in date was delayed, we had to abbreviate the original field plan, which included collections in the Heritage Range (figure 1). We were put in on 21 November 1989 5 kilometers west of Mount Gardner in the central Sentinel Range (figure 2). On this expedition, all samples were collected from quartzites of the Crashsite Group, mainly from the Howard Nunataks Formation (Craddock et al. 1986). Sample size was typically about 5 kilograms. Over the span of 4 days, we collected a "vertical" profile of 26 samples from the Vinson Massif covering 2,500 meters of relief from the summit (4,897 meters) to the head of Nimitz Glacier (1,400 meters). On the first day, we covered the lower ridge line from the terrace to the west of Vinson Massif down to Nimitz Glacier, with access by snowmobile from the west side of the glacier (figure 2). On the second day, we covered the western ridge line of the Vinson Massif from about the 2,900-meter level down to the terrace at the foot of the massif. Access was by snowmobile down a drift on the north of the glacier draining the face of Vinson Massif. On the third day, we drove by snowmobile to the head of this glacier and climbed to the 3,800-meter level of the summit plateau, placing a tent and collecting down from 4,000 meters to the snowmobiles. On the fourth day (30 November), we drove to the head of the glacier, climbed to the tent, where we rested and cooked a meal, and then continued to the summit. From there, we sampled down to the previously collected level. The summit day took 18 hours, basecamp to basecamp. Subsequently, the party traversed down Nimitz Glacier to Bowers Corner (figure 1) collecting on both sides of the glacier. 38
Figure 2
79°S
Bastien Hills
,-Nunatak .690±
Minisa (aCU "
Bowers Corner
elp c3
100 km 1
Figure 1. Location map, Ellsworth Mountains. (km denotes kilometer.) A 400-meter profile (5 samples) was collected at Bowers Corner extending the Vinson profile to the lowest elevation in the Sentinel Range (690 meters). From there, collections were made on the northern side of Minnesota Glacier from Nunatak 690 ANTARCTIC JOURNAL
on the eastern side of the range, to the southern end of the Bastien Hills on the western side (figure 1). On the return traverse to basecamp, we made collections from six localities in the Bastien Hills. Collections were also made from several localities on nunataks and spurs in the vicinity of the basecamp. Our collections from the 1989-1990 austral summer provide a composite vertical profile of the Sentinel Range totalling approximately 3,000 meters, a transverse profile of the range, and a suite of samples surrounding Nimitz Glacier. These samples offer the potential of determining the uplift history of the range, including time of initiation of uplift, average uplift rate, and whether multiple episodes of uplift occurred. Relative displacement across the range, and whether a major fault occurs down Nimitz Glacier also may be determined. Returned samples are being prepared for counting and track length measurements in the Fission Track Dating Laboratory at Arizona State University. This work was supported by National Science Foundation grant DPP 88-0981. Mountaineers Rob Hall and Mugs Stump assisted throughout the field season.
Reference Figure 2. Location map, central Sentinel Range. Snowmobile routes are indicated by dashed lines. Collecting routes are indicated by dotted lines. (km denotes kilometer.)
1990 REVIEW
Craddock, C., G. F. Webers, R. Rutford, B. Sporli and J . J . Anderson. 1986. Geologic map of the Ellsworth Mountains, Antarctica. (Map and Chart Series MC-57). Boulder: Geological Society of America.
39
New vertebrates from the Fremouw formation (Triassic) Beardmore Glacier region, Antarctica. Antarctic Journal of the U.S., 21(5), 24-26. Seeley, H.G. 1894. Researches on the structure, organization and classification of the fossil Reptilia. Part IX, section 1: On the Therosuchia. Philosophical Transactions of the Royal Society of London, series B, 185, 987-1,018.
Field collection for apatite fission track analysis, Ellsworth Mountains
85°W
EDMUND STUMP and PAUL C. FITZGERALD
Department of Geology Arizona State University Tempe, Arizona 85287-1404
We collected rock samples for fission track analysis in the Ellsworth Mountains during the 1989-1990 austral summer to provide an understanding of the tectonic history of this crustal block. In broader terms, the study will attempt to relate the uplift history of the Ellsworth Mountains to the tectonic evolution of West Antarctica. Because the put-in date was delayed, we had to abbreviate the original field plan, which included collections in the Heritage Range (figure 1). We were put in on 21 November 1989 5 kilometers west of Mount Gardner in the central Sentinel Range (figure 2). On this expedition, all samples were collected from quartzites of the Crashsite Group, mainly from the Howard Nunataks Formation (Craddock et al. 1986). Sample size was typically about 5 kilograms. Over the span of 4 days, we collected a "vertical" profile of 26 samples from the Vinson Massif covering 2,500 meters of relief from the summit (4,897 meters) to the head of Nimitz Glacier (1,400 meters). On the first day, we covered the lower ridge line from the terrace to the west of Vinson Massif down to Nimitz Glacier, with access by snowmobile from the west side of the glacier (figure 2). On the second day, we covered the western ridge line of the Vinson Massif from about the 2,900-meter level down to the terrace at the foot of the massif. Access was by snowmobile down a drift on the north of the glacier draining the face of Vinson Massif. On the third day, we drove by snowmobile to the head of this glacier and climbed to the 3,800-meter level of the summit plateau, placing a tent and collecting down from 4,000 meters to the snowmobiles. On the fourth day (30 November), we drove to the head of the glacier, climbed to the tent, where we rested and cooked a meal, and then continued to the summit. From there, we sampled down to the previously collected level. The summit day took 18 hours, basecamp to basecamp. Subsequently, the party traversed down Nimitz Glacier to Bowers Corner (figure 1) collecting on both sides of the glacier. 38
Figure 2
79°S
Bastien Hills
,-Nunatak .690±
Minisa (aCU "
Bowers Corner
elp c3
100 km 1
Figure 1. Location map, Ellsworth Mountains. (km denotes kilometer.) A 400-meter profile (5 samples) was collected at Bowers Corner extending the Vinson profile to the lowest elevation in the Sentinel Range (690 meters). From there, collections were made on the northern side of Minnesota Glacier from Nunatak 690 ANTARCTIC JOURNAL
on the eastern side of the range, to the southern end of the Bastien Hills on the western side (figure 1). On the return traverse to basecamp, we made collections from six localities in the Bastien Hills. Collections were also made from several localities on nunataks and spurs in the vicinity of the basecamp. Our collections from the 1989-1990 austral summer provide a composite vertical profile of the Sentinel Range totalling approximately 3,000 meters, a transverse profile of the range, and a suite of samples surrounding Nimitz Glacier. These samples offer the potential of determining the uplift history of the range, including time of initiation of uplift, average uplift rate, and whether multiple episodes of uplift occurred. Relative displacement across the range, and whether a major fault occurs down Nimitz Glacier also may be determined. Returned samples are being prepared for counting and track length measurements in the Fission Track Dating Laboratory at Arizona State University. This work was supported by National Science Foundation grant DPP 88-0981. Mountaineers Rob Hall and Mugs Stump assisted throughout the field season.
Reference Figure 2. Location map, central Sentinel Range. Snowmobile routes are indicated by dashed lines. Collecting routes are indicated by dotted lines. (km denotes kilometer.)
1990 REVIEW
Craddock, C., G. F. Webers, R. Rutford, B. Sporli and J . J . Anderson. 1986. Geologic map of the Ellsworth Mountains, Antarctica. (Map and Chart Series MC-57). Boulder: Geological Society of America.
39
