Studies of granitic and metamorphic rocks, Horlick and Whitmore ...
This work was supported in part by National Science Foundation grant DPP 88-15976.
References Cook, E.R., and L.A. Kairiukstis (Eds.). 1990. Methods of dendrochronology. Dordrecht: Kluwer Academic Publications. Creber, G.T. 1990. The south polar forest ecosystem. In T.N. Taylor and E.L. Taylor (Ed.), Antarctic paleobiology: Its role in the reconstruction of
Gondwana. New York: Springer-Verlag.
Studies of granitic and metamorphic rocks, Horlick and Whitmore mountains area S.G. BORG, D.J. DEPAOLO, E.E. DALEY, and K.W.W. SIMS Berkeley Center for Isotope Geochemistry Department of Geology and Geophysics University of California Berkeley, California 94720
This paper reports on field work on the granitic and metamorphic basement rocks of the Transantarctic Mountains during the 1990-1991 austral summer. It supplements previous reports in Antarctic Journal (see Borg and DePaolo 1990). Geologic mapping and sampling of granitic and metamorphic rocks were carried out in the Horlick Mountains (including the Wisconsin Range, the Ohio Range, Long Hills, Metavolcanic Mountain, and Minna Spur) and the Whitmore Mountains during the 1990-1991 austral summer. This was accomplished with a combination of Twin Otter support and ground traverses. In early December, a tent camp, including several fuel drums for Twin Otter operations, was placed by LC-130 about 4 kilometers north of Metavolcanic Mountain on the east side of the upper Reedy Glacier (figure) for later occupancy. The field party and geologic field equipment were staged at the Corridor Aerogeophysics of the Southeastern Ross Transect Zone (CASERTZ) camp (figure) for Twin Otter operations. An additional fuel cache was established in the northwestern Horlick Mountains by the Twin Otter crew prior to beginning science support. The Twin Otter was used in a close-support role for reconnaissance geologic mapping and sampling directly from the CASERTZ camp. Although the CASERTZ camp was approximately 1 hour flight time from the nearest outcrop, it provided access to a large segment of the Transantarctic Mountains, from the upper Reedy Glacier to the Whitmore Mountains. In a close-support role, the Twin Otter proved to be ideal for our purposes, providing a large operational area with the ability to land within walking distance of outcrops. About 1,600 kilograms of rock was collected representing all the basement lithologies (79 samples from 46 localities). Our work follows up on reconnaissance studies done in the Horlick Mountains by J. Murtaugh and G. Faure in the late 24
Francis, J. 1986. Growth rings in Cretaceous Tertiary wood from Antarctica and their palaeoclimatic implications. Palaeontology, 29(4), 665684.
Jefferson, T.H. 1982. Fossil forests from the Lower Cretaceous of Alexander Island, Antarctica. Palaeontology, 25(4), 681-708. Spicer, R.A., and J.T. Parrish. 1990. Latest Cretaceous wood of the central North Slope, Alaska. Palaeontology, 33, 225-242. Taylor, E.L. 1989. Tree-ring structure in woody axes from the central Transantarctic Mountains, Antarctica. In Proceedings of the International Symposium on Antarctic Research. (Hangzhou, P.R. China, May 1989.) Tianjin: China Ocean Press.
1960's (Murtaugh 1969; Faure, Murtaugh, and Montigny 1968). Our goal is to characterize the crystalline basement rocks in terms of their neodymium, strontium, and oxygen isotopic compositions and to delineate crustal provinces (see Borg and DePaolo 1990; Borg, DePaolo, and Smith 1990). The basement in the Horlick Mountains region is composed of granitic and metamorphic rocks (see Murtaugh 1969). The metamorphic rocks include both metasedimentary and metaigneous lithologies. At Spear Nunatak in the upper Reedy Glacier area, the metasedimentary rocks are represented by complexly folded amphibolite-grade banded gneisses and schists. This unit is lithologically similar to the Miller Formation in the upper Nimrod Glacier region. In the lower Reedy Glacier area, metasedimentary rocks are represented by greenschist facies graywacke-shale sequences, probably equivalent to the LaGorce Formation. Metaigneous rocks are represented by dacitic porphyritic volcanic rocks, probably Wyatt Formation, exposed at Metavolcanic Mountain, in the Mims Spur region, and in the Long Hills. Granitic rocks that have intruded these metamorphic rocks range from granite to granodiorite and include deformed and undeformed lithologies. The deformed lithologies are associated with well-developed shear zones, and there is no compelling field evidence to suggest that any of these granites are significantly older than the undeformed lithologies. All of the granites in the Horlick Mountains are probably associated with the Cambro-Ordovician Ross Orogeny. Analytical work is underway to characterize the granites and metamorphic units. This will allow us to trace basement provinces delineated in the Nimrod-Shackleton Glaciers region toward the southeast in the Transantarctic Mountains. We would like to thank National Science Foundation Polar Operations, Kenn Borek Air Ltd., VXE-6, and Antarctic Support Associates, Inc., for their efforts in support of our field work. Special thanks go to Henry Perk, Jim Pearce, and Doug Gaunt of Kenn Borek Air Ltd., and to Kevin Killilea (manager of the CASERTZ camp) and Rick Campbell (field party liaison) of Antarctic Support Associates. This research was supported by National Science Foundation grant DPP 88-16925.
References Borg, 5G., and D.J. DePaolo. 1990. Crustal basement provinces of the Transantarctic Mountains, Ross Sea sector. Antarctic Journal of the U.S., 25(5), 29-31.
Borg, 5G., D.J. DePaolo, and B.M. Smith. 1990. Isotopic structure and tectonics of the central Transantarctic Mountains. Journal of Geophysical Research, 95(135), 6647-6667.
ANTARCTIC JOURNAL
Faure, G., J.G. Murtaugh, and R.J.E. Montigny. 1968. The geology and geochronology of the basement complex of the central Transantarctic Mountains. Canadian Journal of Earth Sciences, 5, 555-560.
Murtaugh, J.G. 1969. Geology of the Wisconsin Range Batholith, Transantarctic Mountains. New Zealand Journal of Geology and Geophysics, 12(2&3), 526-550.
SP Antarctica
Northern Victoria Land
CO
I
I I I I
0 kilometers 300 I I I
0 miles 200
TI
Ross Sea
Southern V 1..#LUI IQ
OU
Land
cMurdo Station 180' + 80'S
Byrd Glacier
/ Ross Ice Shelf
çjC
Central
Nimrod Glacier Beardmore Glacier
Antarctic Ice Sheet
Shackleton Glacier
Transantarctic
Marie Byrd Land
IS
I Scott Glacier IQ
Reedy Glacier
East Antarctic Ice Sheet
CASE RTZ 0
Mountains Wisconsin Range Camp
Light gray shading shows outcrop area in the Transantarctic Mountains. +
Samples are now Whitmore being processed from this region. Mtns
South Pole
Thiel Mtns
Locations in the Transantarctic Mountains.
1991 REVIEW
25
References Cook, E.R., and L.A. Kairiukstis (Eds.). 1990. Methods of dendrochronology. Dordrecht: Kluwer Academic Publications. Creber, G.T. 1990. The south polar forest ecosystem. In T.N. Taylor and E.L. Taylor (Ed.), Antarctic paleobiology: Its role in the reconstruction of
Gondwana. New York: Springer-Verlag.
Studies of granitic and metamorphic rocks, Horlick and Whitmore mountains area S.G. BORG, D.J. DEPAOLO, E.E. DALEY, and K.W.W. SIMS Berkeley Center for Isotope Geochemistry Department of Geology and Geophysics University of California Berkeley, California 94720
This paper reports on field work on the granitic and metamorphic basement rocks of the Transantarctic Mountains during the 1990-1991 austral summer. It supplements previous reports in Antarctic Journal (see Borg and DePaolo 1990). Geologic mapping and sampling of granitic and metamorphic rocks were carried out in the Horlick Mountains (including the Wisconsin Range, the Ohio Range, Long Hills, Metavolcanic Mountain, and Minna Spur) and the Whitmore Mountains during the 1990-1991 austral summer. This was accomplished with a combination of Twin Otter support and ground traverses. In early December, a tent camp, including several fuel drums for Twin Otter operations, was placed by LC-130 about 4 kilometers north of Metavolcanic Mountain on the east side of the upper Reedy Glacier (figure) for later occupancy. The field party and geologic field equipment were staged at the Corridor Aerogeophysics of the Southeastern Ross Transect Zone (CASERTZ) camp (figure) for Twin Otter operations. An additional fuel cache was established in the northwestern Horlick Mountains by the Twin Otter crew prior to beginning science support. The Twin Otter was used in a close-support role for reconnaissance geologic mapping and sampling directly from the CASERTZ camp. Although the CASERTZ camp was approximately 1 hour flight time from the nearest outcrop, it provided access to a large segment of the Transantarctic Mountains, from the upper Reedy Glacier to the Whitmore Mountains. In a close-support role, the Twin Otter proved to be ideal for our purposes, providing a large operational area with the ability to land within walking distance of outcrops. About 1,600 kilograms of rock was collected representing all the basement lithologies (79 samples from 46 localities). Our work follows up on reconnaissance studies done in the Horlick Mountains by J. Murtaugh and G. Faure in the late 24
Francis, J. 1986. Growth rings in Cretaceous Tertiary wood from Antarctica and their palaeoclimatic implications. Palaeontology, 29(4), 665684.
Jefferson, T.H. 1982. Fossil forests from the Lower Cretaceous of Alexander Island, Antarctica. Palaeontology, 25(4), 681-708. Spicer, R.A., and J.T. Parrish. 1990. Latest Cretaceous wood of the central North Slope, Alaska. Palaeontology, 33, 225-242. Taylor, E.L. 1989. Tree-ring structure in woody axes from the central Transantarctic Mountains, Antarctica. In Proceedings of the International Symposium on Antarctic Research. (Hangzhou, P.R. China, May 1989.) Tianjin: China Ocean Press.
1960's (Murtaugh 1969; Faure, Murtaugh, and Montigny 1968). Our goal is to characterize the crystalline basement rocks in terms of their neodymium, strontium, and oxygen isotopic compositions and to delineate crustal provinces (see Borg and DePaolo 1990; Borg, DePaolo, and Smith 1990). The basement in the Horlick Mountains region is composed of granitic and metamorphic rocks (see Murtaugh 1969). The metamorphic rocks include both metasedimentary and metaigneous lithologies. At Spear Nunatak in the upper Reedy Glacier area, the metasedimentary rocks are represented by complexly folded amphibolite-grade banded gneisses and schists. This unit is lithologically similar to the Miller Formation in the upper Nimrod Glacier region. In the lower Reedy Glacier area, metasedimentary rocks are represented by greenschist facies graywacke-shale sequences, probably equivalent to the LaGorce Formation. Metaigneous rocks are represented by dacitic porphyritic volcanic rocks, probably Wyatt Formation, exposed at Metavolcanic Mountain, in the Mims Spur region, and in the Long Hills. Granitic rocks that have intruded these metamorphic rocks range from granite to granodiorite and include deformed and undeformed lithologies. The deformed lithologies are associated with well-developed shear zones, and there is no compelling field evidence to suggest that any of these granites are significantly older than the undeformed lithologies. All of the granites in the Horlick Mountains are probably associated with the Cambro-Ordovician Ross Orogeny. Analytical work is underway to characterize the granites and metamorphic units. This will allow us to trace basement provinces delineated in the Nimrod-Shackleton Glaciers region toward the southeast in the Transantarctic Mountains. We would like to thank National Science Foundation Polar Operations, Kenn Borek Air Ltd., VXE-6, and Antarctic Support Associates, Inc., for their efforts in support of our field work. Special thanks go to Henry Perk, Jim Pearce, and Doug Gaunt of Kenn Borek Air Ltd., and to Kevin Killilea (manager of the CASERTZ camp) and Rick Campbell (field party liaison) of Antarctic Support Associates. This research was supported by National Science Foundation grant DPP 88-16925.
References Borg, 5G., and D.J. DePaolo. 1990. Crustal basement provinces of the Transantarctic Mountains, Ross Sea sector. Antarctic Journal of the U.S., 25(5), 29-31.
Borg, 5G., D.J. DePaolo, and B.M. Smith. 1990. Isotopic structure and tectonics of the central Transantarctic Mountains. Journal of Geophysical Research, 95(135), 6647-6667.
ANTARCTIC JOURNAL
Faure, G., J.G. Murtaugh, and R.J.E. Montigny. 1968. The geology and geochronology of the basement complex of the central Transantarctic Mountains. Canadian Journal of Earth Sciences, 5, 555-560.
Murtaugh, J.G. 1969. Geology of the Wisconsin Range Batholith, Transantarctic Mountains. New Zealand Journal of Geology and Geophysics, 12(2&3), 526-550.
SP Antarctica
Northern Victoria Land
CO
I
I I I I
0 kilometers 300 I I I
0 miles 200
TI
Ross Sea
Southern V 1..#LUI IQ
OU
Land
cMurdo Station 180' + 80'S
Byrd Glacier
/ Ross Ice Shelf
çjC
Central
Nimrod Glacier Beardmore Glacier
Antarctic Ice Sheet
Shackleton Glacier
Transantarctic
Marie Byrd Land
IS
I Scott Glacier IQ
Reedy Glacier
East Antarctic Ice Sheet
CASE RTZ 0
Mountains Wisconsin Range Camp
Light gray shading shows outcrop area in the Transantarctic Mountains. +
Samples are now Whitmore being processed from this region. Mtns
South Pole
Thiel Mtns
Locations in the Transantarctic Mountains.
1991 REVIEW
25
