Triassic tetrapods from McGregor Glacier
References Baker, P. E. In Press. Recent volcanism and magmatic variation in the Scotia Arc. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Bentley, C. R., and J . W. Clough. In press. Seismic refraction measurements of antarctic subglacial structure. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Craddock, C. In press. Antarctic tectonics. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Craddock, C., T. W. Bastien, and R. H. Rutford. 1963. Geology of the Jones Mountains area. In: Antarctic Geology. Amsterdam, North-Holland. p. 171-187. Halpern, M. 1968. Ages of antarctic and Argentine rocks bearing on continental drift. Earth and Planetary Science Letters, 5: 159-167. Laudon, T. S. In press. The stratigraphy of eastern Ells-
worth Land. In: Antarctic Geology and Geophysics. Oslo,
Universitetsforlaget. LeMasurier, W. E. 1970. Tectonic environment of circumPacific volcanism in Marie Byrd Land, Antarctica (abstract). American Geophysical Union. Transactions, 51: 824. LeMasurier, W. E. In press. Volcanic record of Cenozoic glacial history in Marie Byrd Land. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. LeMasurier, W. E., and F. Alton Wade. 1968. Fumarolic activity in Marie Byrd Land, Antarctica. Science, 162: 352. Lipman, P. W. 1969. Alkalic and tholeiitic basaltic volcanism related to the Rio Grande depression, southern Colorado and northern New Mexico. Geological Society of America. Bulletin, 80: 1343-1354. Mohr, P. A. 1971. Ethiopian rift and plateaus: some volcanic petrochemical differences. Journal of Geophysical Research, 76: 197-1984. Moore, James G. 1970. Water content of basalt erupted on
the ocean floor. Contributions to Mineralogy and Petrology,
28: 272-279. Wade, F. A., and K. E. LaPrade. 1969. Geology of the King Peninsula, Canisteo Peninsula, and Hudson Mountains areas, Ellsworth Land, Antarctica. Antarctic Journal of the U.S., IV(4): 92-93. Wade, F. A., and J . R. Wilbanks. In press. The geology of Marie Byrd Land and Ellsworth Land, Antarctica. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Warner, L. A. .1945. Structure and petrography of the southern Edsel Ford Ranges, Antarctica. American Philosophical Society. Proceedings, 89: 78-122.
Triassic tetrapods from McGregor Glacier EDWIN H. COLBERT
Museum of Northern Arizona During the antarctic field season of 1969-1970, as readers will recall, a considerable collection of Lower Triassic tetrapods was made from the Fremouw Formation at Coalsack Bluff in the Transantarctic Mountains, immediately to the east of the Beardmore Gla188
Labyrinthodont amphibian skull from McGregor Glacier area.
cier. It had been intended to extend the work of that season to the region of McGregor Glacier, some 240 km distant, but weather and circumstances prevented it. Consequently, this aspect of the field campaign was resumed during the 1970-1971 season. Paleontological prospecting and collecting was carried on by Mr. James W. Kitching of the Bernard Price Institute for Palontology, University of the Witwatersrand, Johannesburg, South Africa, assisted by Mr. John Ruben of the University of California at Berkeley, and for a short time by Mr. Thomas Rich of the American Museum of Natural History in New York. It had been hoped that well preserved fossils would be found in the McGregor Glacier region, since previous studies had indicated that this area was up the paleoslope from Coalack Bluff, and thus might be close to the source of fossil burials. The hope was fully justified: whereas at Coalsack Bluff the fossils, though numerous, consisted of isolated and rolled bones deposited in coarse sands and even conglomerates, at McGregor Glacier the specimens consisted of articulated skeletons and partial skeletons contained within rather fine-grained siltstones (see photo). As a result, our knowledge of early Triassic antarctic tetrapods has been augmented and expanded. The work of this past season was aided by good weather, a contrast to the inclement weather that plagued the paleontologists during the previous collecting field season. The initial fossil of this past season, an imprint of a complete skeleton of the mammal-like reptile Thri naxodon, was found on the first day in the field Dr. James Collinson of The Ohio State University, ANTARCTIC JOURNAL
From that time until the termination of work, fossils were found plentifully exposed in the McGregor Glacier region and so far as time permitted were collected. Several promising areas were located for future xploration and development. In this connection, a isit was made to Graphite Peak, where the first tetrapod fossil from Antarctica, a fragment of an amphibian jaw, had been found by Peter Barrett in 1967, and umerous bones of Lystrosaurus were seen there. The collection of this past season added additional materials of the dicynodont reptile Lystrosaurus to t ose already collected in Antarctica. This is the genus characteristic of the Lower Triassic Lystrosaurus e in South Africa as well as of Lower Triassic sedionrits in India and in China. Also, labyrinthodont phibians and small thecodont reptiles, found durtt the previous field season, were collected at McGregor Glacier. But of particular significance was the discovery at McGregor Glacier of various tetrapods that previously had not been found in Antarctica. The genus Thriraxodon, a form quite typical of the South African deposits, has already been mentioned. This important genus is represented by several specimens. Other mammal-like reptiles, still to be identified, were found. Several skeletons of the cotylosaurian reptile Procolophon, again a genus characteristic of the South African Lystrosaurus zone, were collected. Finally, a
number of specimens of eosuchians, evidently closely related to the African proto-lizards Prolacerta and Pricea, were discovered and collected. Such reptiles are rare in the Lystrosaurus zone of South Africa; they would appear to be reasonably abundant in the Fremouw Formation of Antarctica. The collections of the past field season strengthen the paleontological ties between Antarctica and Africa during early Triassic time. They indicate, beyond much doubt, that there was a very close connection between the two present-day continents, a connection that was sufficiently broad to allow the free interchange of complete faunas between the two areas. In short, Africa and Antarctica were parts of a single continent, as clearly indicated by the full representation of the Lystrosaurus fauna in the Karroo Basin of South Africa and in the Transantarctic Mountains, some 600 km from the South Pole. The significance of this fact in the interpretation of Gondwanaland and the study of continental drift is obvious. The fossil tetrapods from Antarctica are now at the Museum of Northern Arizona in Flagstaff, where they are being studied by E. H. Colbert, assisted by a grant from the National Science Foundation. Mr. Kitching worked in Antarctica at the invitation of the National Science Foundation, and he was also supported in part by the Council of Scientific and Industrial Research of the Republic of South Africa.
Permian stromatolites from Coalsack Col
Precambrian stromatolites found by Dr. Campbell Craddock in the Thiel Mountains. The stromatolites were found in three zones of the Buckley Formation (Permian). The same formation nearby also contains coal seams up to several feet thick and leaves of the characteristic Gondwana plant Glossopteris. The Buckley Formation is generally considered to have been deposited in a slowly subsiding flood plain with ephemeral lakes and swamps and meandering streams that flowed generally to the east and south. The algae probably flourished in the ephemeral lakes, although many stromatolites have
so
WILLIAM J . BREED
Museum of Northern Arizona Stromatolites (generally considered to be fossil algae) were found in 1969 at Coalsack Col,* 1 km southwest of Coalsack Bluff. This is the first report of their presence in Antarctica with the exception of the name. V.' .
lL-! Figure 1. Weathered side of stromatolite Figure 2. Weathered top surface of stro- Figure 3. Stromatolite zone on top of block. matolite block, siliceous fine-grained block.
September—October 1971
189
worth Land. In: Antarctic Geology and Geophysics. Oslo,
Universitetsforlaget. LeMasurier, W. E. 1970. Tectonic environment of circumPacific volcanism in Marie Byrd Land, Antarctica (abstract). American Geophysical Union. Transactions, 51: 824. LeMasurier, W. E. In press. Volcanic record of Cenozoic glacial history in Marie Byrd Land. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. LeMasurier, W. E., and F. Alton Wade. 1968. Fumarolic activity in Marie Byrd Land, Antarctica. Science, 162: 352. Lipman, P. W. 1969. Alkalic and tholeiitic basaltic volcanism related to the Rio Grande depression, southern Colorado and northern New Mexico. Geological Society of America. Bulletin, 80: 1343-1354. Mohr, P. A. 1971. Ethiopian rift and plateaus: some volcanic petrochemical differences. Journal of Geophysical Research, 76: 197-1984. Moore, James G. 1970. Water content of basalt erupted on
the ocean floor. Contributions to Mineralogy and Petrology,
28: 272-279. Wade, F. A., and K. E. LaPrade. 1969. Geology of the King Peninsula, Canisteo Peninsula, and Hudson Mountains areas, Ellsworth Land, Antarctica. Antarctic Journal of the U.S., IV(4): 92-93. Wade, F. A., and J . R. Wilbanks. In press. The geology of Marie Byrd Land and Ellsworth Land, Antarctica. In: Antarctic Geology and Geophysics. Oslo, Universitetsforlaget. Warner, L. A. .1945. Structure and petrography of the southern Edsel Ford Ranges, Antarctica. American Philosophical Society. Proceedings, 89: 78-122.
Triassic tetrapods from McGregor Glacier EDWIN H. COLBERT
Museum of Northern Arizona During the antarctic field season of 1969-1970, as readers will recall, a considerable collection of Lower Triassic tetrapods was made from the Fremouw Formation at Coalsack Bluff in the Transantarctic Mountains, immediately to the east of the Beardmore Gla188
Labyrinthodont amphibian skull from McGregor Glacier area.
cier. It had been intended to extend the work of that season to the region of McGregor Glacier, some 240 km distant, but weather and circumstances prevented it. Consequently, this aspect of the field campaign was resumed during the 1970-1971 season. Paleontological prospecting and collecting was carried on by Mr. James W. Kitching of the Bernard Price Institute for Palontology, University of the Witwatersrand, Johannesburg, South Africa, assisted by Mr. John Ruben of the University of California at Berkeley, and for a short time by Mr. Thomas Rich of the American Museum of Natural History in New York. It had been hoped that well preserved fossils would be found in the McGregor Glacier region, since previous studies had indicated that this area was up the paleoslope from Coalack Bluff, and thus might be close to the source of fossil burials. The hope was fully justified: whereas at Coalsack Bluff the fossils, though numerous, consisted of isolated and rolled bones deposited in coarse sands and even conglomerates, at McGregor Glacier the specimens consisted of articulated skeletons and partial skeletons contained within rather fine-grained siltstones (see photo). As a result, our knowledge of early Triassic antarctic tetrapods has been augmented and expanded. The work of this past season was aided by good weather, a contrast to the inclement weather that plagued the paleontologists during the previous collecting field season. The initial fossil of this past season, an imprint of a complete skeleton of the mammal-like reptile Thri naxodon, was found on the first day in the field Dr. James Collinson of The Ohio State University, ANTARCTIC JOURNAL
From that time until the termination of work, fossils were found plentifully exposed in the McGregor Glacier region and so far as time permitted were collected. Several promising areas were located for future xploration and development. In this connection, a isit was made to Graphite Peak, where the first tetrapod fossil from Antarctica, a fragment of an amphibian jaw, had been found by Peter Barrett in 1967, and umerous bones of Lystrosaurus were seen there. The collection of this past season added additional materials of the dicynodont reptile Lystrosaurus to t ose already collected in Antarctica. This is the genus characteristic of the Lower Triassic Lystrosaurus e in South Africa as well as of Lower Triassic sedionrits in India and in China. Also, labyrinthodont phibians and small thecodont reptiles, found durtt the previous field season, were collected at McGregor Glacier. But of particular significance was the discovery at McGregor Glacier of various tetrapods that previously had not been found in Antarctica. The genus Thriraxodon, a form quite typical of the South African deposits, has already been mentioned. This important genus is represented by several specimens. Other mammal-like reptiles, still to be identified, were found. Several skeletons of the cotylosaurian reptile Procolophon, again a genus characteristic of the South African Lystrosaurus zone, were collected. Finally, a
number of specimens of eosuchians, evidently closely related to the African proto-lizards Prolacerta and Pricea, were discovered and collected. Such reptiles are rare in the Lystrosaurus zone of South Africa; they would appear to be reasonably abundant in the Fremouw Formation of Antarctica. The collections of the past field season strengthen the paleontological ties between Antarctica and Africa during early Triassic time. They indicate, beyond much doubt, that there was a very close connection between the two present-day continents, a connection that was sufficiently broad to allow the free interchange of complete faunas between the two areas. In short, Africa and Antarctica were parts of a single continent, as clearly indicated by the full representation of the Lystrosaurus fauna in the Karroo Basin of South Africa and in the Transantarctic Mountains, some 600 km from the South Pole. The significance of this fact in the interpretation of Gondwanaland and the study of continental drift is obvious. The fossil tetrapods from Antarctica are now at the Museum of Northern Arizona in Flagstaff, where they are being studied by E. H. Colbert, assisted by a grant from the National Science Foundation. Mr. Kitching worked in Antarctica at the invitation of the National Science Foundation, and he was also supported in part by the Council of Scientific and Industrial Research of the Republic of South Africa.
Permian stromatolites from Coalsack Col
Precambrian stromatolites found by Dr. Campbell Craddock in the Thiel Mountains. The stromatolites were found in three zones of the Buckley Formation (Permian). The same formation nearby also contains coal seams up to several feet thick and leaves of the characteristic Gondwana plant Glossopteris. The Buckley Formation is generally considered to have been deposited in a slowly subsiding flood plain with ephemeral lakes and swamps and meandering streams that flowed generally to the east and south. The algae probably flourished in the ephemeral lakes, although many stromatolites have
so
WILLIAM J . BREED
Museum of Northern Arizona Stromatolites (generally considered to be fossil algae) were found in 1969 at Coalsack Col,* 1 km southwest of Coalsack Bluff. This is the first report of their presence in Antarctica with the exception of the name. V.' .
lL-! Figure 1. Weathered side of stromatolite Figure 2. Weathered top surface of stro- Figure 3. Stromatolite zone on top of block. matolite block, siliceous fine-grained block.
September—October 1971
189
