Seymour Island expedition, 1986-1987 Simple Storage
Pankhurst, R.J. 1980. Radiometric dating (appendix). In D.C. Singleton (Ed.), The geology of the central Black Coast, Palmer Land. (British Antarctic Survey Science Reports, No. 102.) Cambridge: British Antarctic Survey. Rowley, PD., K.S. Kellogg, and W.R. Vennum. 1985. Geologic studies in the English Coast, eastern Ellsworth Land, Antarctica. Antarctic Journal of the U.S., 19(5), 34-36.
Rowley, PD., K.S. Kellogg, W.R. Vennum, R.B. Waitt, and S.J. Boyer. 1987. Geology of the southern Black Coast, Antarctic Peninsula. In P.D. Rowley and W.R. Vennum (Eds.), Studies of the geology and mineral resources of the southern Antarctic Peninsula and eastern Ellsworth Land, Antarctica. (U.S. Geological Survey Professional Paper 1351.) Wash-
ington: U.S. Government Printing Office. Rowley, RD., D.L. Schmidt, and P.L. Williams. 1982. Mount Poster Formation, southern Antarctic Peninsula and eastern Ellsworth Land. Antarctic Journal of the U.S., 17(5), 38-39.
Rowley, PD., W.R. Vennum, K.S. Kellogg, T.S. Laudon, P.E. Carrara, J.M. Boyles, and M.R.A. Thomson. 1983. Geology and plate tectonic setting of the Orville Coast and eastern Ellsworth Land, Antarctica. In R.L. Oliver, P.R. James, and J.B. Jago (Eds.), Antarctic cart/i science. Canberra: Australian Academy of Science.
Seymour Island expedition, 1986-1987 WILLIAM
J. ZINSMEISTER
Department of Earth and Atmospheric Sciences Purdue University West Lafayette, Indiana 47907
The expedition to Seymour Island on the northeast tip of the Antarctic Peninsula during December and January of the 1986-1987 austral summer marks the fourth major field effort to Seymour Island sponsored by the National Science Foundation's Division of Polar Programs (Zinsmeister 1982, 1985). As with the previous three expeditions (1981, 1984, and 1985), this year's expedition resulted in a number of major paleontologic and geologic discoveries which are providing new insight, not only into the geologic history of the Antarctic Peninsula but also to our understanding of the climatic and biogeographic history of the Southern Hemisphere. Because of past discoveries, a large party (12 scientists and a camp manager) was sent to Seymour Island. The party consisted of William J. Zinsmeister, Chief Scientist, Purdue University; Rodney M. Feldmann, Kent State University; David H. Elliot, Ohio State University; and M.O. Woodburne, M.A. Kooser, and Judd Case, University of California, Riverside. In addition to the senior personnel, Jeff Stilwell, Dan Chaney, Fred Barbis, and Tim Kelley served as field assistants to the science programs. Rob Robbins, Antarctic Services, acted as camp manager during the season. In contrast to the 1985 season which was conducted from the K/v Polar Duke without helicopter support, this season was supported by the Coast Guard icebreaker USCGC Glacier. Support by the USCGC Glacier allowed for the extensive use of the Coast Guard helicopters which enabled members of the field party to conduct field work on James Ross, Vega, and Cockburn islands. 1987
REVIEW
Rowley, RD., and P.L. Williams. 1982. Geology of the northern Lassiter Coast and southern Black Coast, Antarctic Peninsula. In C. Craddock (Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Singleton, D.C. 1980. The geology of the central Black Coast, Palmer Land. (British Antarctic Survey Scientific Reports, No. 102.) Cambridge: British
Antarctic Survey. Storey, B.C., and S.W. Garrett. 1985. Crustal growth of the Antarctic Peninsula by accretion, magmatism and extension. Geology Magazine, 122(1), 5-14.
Suárez, M. 1976. Plate-tectonic model for southern Antarctic Peninsula and its relation to southern Andes. Geology, 4, 211-214. Thomson, M.R.A. 1982. Mesozoic paleogeography of West Antarctica. In C. Craddock (Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Vennum, W.R., and P.D. Rowley. 1986. Reconnaissance geochemistry of the Lassiter Coast Intrusive Suite, southern Antarctic Peninsula. Geological Society of America Bulletin, 97, 1521-1533.
Williams, RL., D.L. Schmidt, C.C. Plummer, and L.E. Brown. 1972. Geology of the Lassiter Coast area, Antarctic Peninsula: Preliminary report. In R.J. Adie (Ed.), Antarctic geology and geophysics. Oslo:
Universitetsforlaget.
The primary objectives of field party were to make a detailed survey of the faunal changes across the Cretaceous/Tertiary (K/T) boundary and to search for additional vertebrate fossils in the Late Eocene part of the sequence at the north end of the island. As a consequence, two camps were established: a primary camp at the south end of the island to study the KIT part of the sequence and a northern camp for vertebrate fossil program. The use of the four-wheel, all-terrain vehicle allowed for travel and movement of supplies and personnel between the two camps. In contrast to the 1985 season, weather conditions were ideal and only a total of I day was lost to poor weather. As a consequence to the excellent weather conditions that prevailed, a number of important scientific discoveries was made during the season. The highlights of the field season are summarized here. • A nearly complete basiliosaurine whale skeleton in the Upper Eocene La Meseta Formation was discovered. This specimen represents the oldest occurrence and most complete specimen of a Late Eocene whale discovered in the Southern Hemisphere. • Partial jaw fragment of a large crocodile from the La Meseta Formation. • Skeletal elements of large phororhacoid (large land bird), which attained a height of approximately 2 meters, were found. The occurrence of this land bird, together with the crocodile remains, provides additional evidence of a continuous land connection between southern South America during the early Tertiary. • Stratigraphic study of the KIT shallow-water sequence on Seymour Island is unique, because deposition across the sequence was continuous, whereas other shallow-water K/T sections are characterized either by a hiatus or a condensed section. • Preliminary analysis of the macrofossil fauna across the K/T boundary indicates that in contrast to other K/T boundary sections, there is no abrupt change in the marine benthic fauna but rather a gradual transition over approximately 40 meters of section which includes the boundary.
• A number of ammonites were collected above the KIT boundary as defined by dinocysts. This apparent diachroneity of the KIT boundary between different groups of marine organisms highlights the problem of no formalized definition of the KIT boundary and illustrates the problem of defining the KIT boundary in a section where there was continuous deposition. This research was supported by National Science Foundation grant DPP 84-16783.
New fossil vertebrates from Seymour Island, Antarctic Peninsula MICHAEL 0. WOODBURNE and JUDD A. CASE, Department of Earth Sciences University of California Riverside, California 92521
DAN S. CHANEY U.S. National Museum Smithsonian institution Washington, D.C. 20560
The 1986-1987 field season on Seymour Island (figure 1) yielded new remains of an extinct whale, a large flightless
SOBRAL FM
H1
RV-82001
SEYMOUR IS.
A.
I
L/ MESETA + + FM.
/ RV-8405 CROSS VALLEY FM
LOPEZ de BE RTODANO FORMATION SOBR NNNNNNNNN FM
I I I I I 0 I 2 3 4 5 K
Figure 1. Map of Seymour Island and the Antarctic Peninsula region. The La Meseta Formation is of late Eocene age. All other rock units are older (Late Cretaceous to Paleocene). Fossil localities produced marsupials, crocodiles, and plants (RV-8200) and the phororhacoid bird (RV-8405). The whale site is just below the "F" in La Meseta Formation. ("Km" denotes "kilometer?' "Fm?' denotes "formation.")
References Zinsmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S. 17(5), 63-64. Zinsmeister, W.J. 1985. 1985 Seymour Island Expedition. Antarctic Journal of the U.S. 19(5), 41-42.
terrestrial bird, the first postcranial skeleton of a penguin-like bird, and a lower mandible of a small crocodilian. All of the fossils were recovered from the La Meseta Formation of late Eocene age (approximately 40 million years old). The whale material comprises part of the skull and the vertebrae and ribs of much of the thoracic region. The material is well preserved and shows that it pertains to a basiliosaurine, a member of the archaeocete (ancient-toothed whale) group. According to Ewan Fordyce, University of Otago, New Zealand, who collected the specimens, these remains constitute the best documentation of this kind of whale in the Southern Hemisphere. The animal, which apparently lived in shallow marine waters, may have been about 10 meters long. The specimens are now under study by Fordyce. A wide variety of nominally marine penguin-type birds has been recovered in this and past seasons from Seymour Island. The partial postcranial skeleton recovered this time will enhance functional comparisons between these ancient birds and their modern counterparts. A large (about 2 meters tall), predaceous terrestrial (flightless) bird that apparently pertains to the phororhacoid group lived on Seymour Island in the late Eocene, as shown by a portion of its beak recovered this season (Case, Woodburne, and Chaney in press-a). The group is also known from South America, from the Oligocene to the present (Marshall 1978). Although modern representatives are about the size of a road-runner, the ancient birds were of large size and apparently filled the ecological niche of a large carnivore in the Eocene and Oligocene. Although the legs were relatively slender, the body and head were massive, as shown in reconstructions based on South American fossils (figure 2). The Seymour Island material pre-dates the known age of the group in South America, and some of the bird footprints reported from yet earlier Eocene (approximately 46 million years ago) rocks on King George Island (Covacevich and Rich 1982; Watts 1982) may pertain to this group, as well. In any case, the presence of such derived birds in the american and antarctic Southern Hemisphere indicates that their ancestors must have inhabited this region well before the time the fossils reported here were preserved. Furthermore, the flightless nature of these birds requires a solid overland pathway by which they dispersed between South America and peninsular Antarctica. This strengthens the proposals made earlier (Woodburne and Zinsmeister 1984; Case, Woodburne, and Chaney in press-b) for the existence of such a land connection, based on the presence in La Meseta rocks of two kinds of marsupials and Not hofagus (southern beech) plants. The presence in these same deposits of small crocodiles is consistent with this proposal, ANTARCTIC JOURNAL
Rowley, PD., K.S. Kellogg, W.R. Vennum, R.B. Waitt, and S.J. Boyer. 1987. Geology of the southern Black Coast, Antarctic Peninsula. In P.D. Rowley and W.R. Vennum (Eds.), Studies of the geology and mineral resources of the southern Antarctic Peninsula and eastern Ellsworth Land, Antarctica. (U.S. Geological Survey Professional Paper 1351.) Wash-
ington: U.S. Government Printing Office. Rowley, RD., D.L. Schmidt, and P.L. Williams. 1982. Mount Poster Formation, southern Antarctic Peninsula and eastern Ellsworth Land. Antarctic Journal of the U.S., 17(5), 38-39.
Rowley, PD., W.R. Vennum, K.S. Kellogg, T.S. Laudon, P.E. Carrara, J.M. Boyles, and M.R.A. Thomson. 1983. Geology and plate tectonic setting of the Orville Coast and eastern Ellsworth Land, Antarctica. In R.L. Oliver, P.R. James, and J.B. Jago (Eds.), Antarctic cart/i science. Canberra: Australian Academy of Science.
Seymour Island expedition, 1986-1987 WILLIAM
J. ZINSMEISTER
Department of Earth and Atmospheric Sciences Purdue University West Lafayette, Indiana 47907
The expedition to Seymour Island on the northeast tip of the Antarctic Peninsula during December and January of the 1986-1987 austral summer marks the fourth major field effort to Seymour Island sponsored by the National Science Foundation's Division of Polar Programs (Zinsmeister 1982, 1985). As with the previous three expeditions (1981, 1984, and 1985), this year's expedition resulted in a number of major paleontologic and geologic discoveries which are providing new insight, not only into the geologic history of the Antarctic Peninsula but also to our understanding of the climatic and biogeographic history of the Southern Hemisphere. Because of past discoveries, a large party (12 scientists and a camp manager) was sent to Seymour Island. The party consisted of William J. Zinsmeister, Chief Scientist, Purdue University; Rodney M. Feldmann, Kent State University; David H. Elliot, Ohio State University; and M.O. Woodburne, M.A. Kooser, and Judd Case, University of California, Riverside. In addition to the senior personnel, Jeff Stilwell, Dan Chaney, Fred Barbis, and Tim Kelley served as field assistants to the science programs. Rob Robbins, Antarctic Services, acted as camp manager during the season. In contrast to the 1985 season which was conducted from the K/v Polar Duke without helicopter support, this season was supported by the Coast Guard icebreaker USCGC Glacier. Support by the USCGC Glacier allowed for the extensive use of the Coast Guard helicopters which enabled members of the field party to conduct field work on James Ross, Vega, and Cockburn islands. 1987
REVIEW
Rowley, RD., and P.L. Williams. 1982. Geology of the northern Lassiter Coast and southern Black Coast, Antarctic Peninsula. In C. Craddock (Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Singleton, D.C. 1980. The geology of the central Black Coast, Palmer Land. (British Antarctic Survey Scientific Reports, No. 102.) Cambridge: British
Antarctic Survey. Storey, B.C., and S.W. Garrett. 1985. Crustal growth of the Antarctic Peninsula by accretion, magmatism and extension. Geology Magazine, 122(1), 5-14.
Suárez, M. 1976. Plate-tectonic model for southern Antarctic Peninsula and its relation to southern Andes. Geology, 4, 211-214. Thomson, M.R.A. 1982. Mesozoic paleogeography of West Antarctica. In C. Craddock (Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Vennum, W.R., and P.D. Rowley. 1986. Reconnaissance geochemistry of the Lassiter Coast Intrusive Suite, southern Antarctic Peninsula. Geological Society of America Bulletin, 97, 1521-1533.
Williams, RL., D.L. Schmidt, C.C. Plummer, and L.E. Brown. 1972. Geology of the Lassiter Coast area, Antarctic Peninsula: Preliminary report. In R.J. Adie (Ed.), Antarctic geology and geophysics. Oslo:
Universitetsforlaget.
The primary objectives of field party were to make a detailed survey of the faunal changes across the Cretaceous/Tertiary (K/T) boundary and to search for additional vertebrate fossils in the Late Eocene part of the sequence at the north end of the island. As a consequence, two camps were established: a primary camp at the south end of the island to study the KIT part of the sequence and a northern camp for vertebrate fossil program. The use of the four-wheel, all-terrain vehicle allowed for travel and movement of supplies and personnel between the two camps. In contrast to the 1985 season, weather conditions were ideal and only a total of I day was lost to poor weather. As a consequence to the excellent weather conditions that prevailed, a number of important scientific discoveries was made during the season. The highlights of the field season are summarized here. • A nearly complete basiliosaurine whale skeleton in the Upper Eocene La Meseta Formation was discovered. This specimen represents the oldest occurrence and most complete specimen of a Late Eocene whale discovered in the Southern Hemisphere. • Partial jaw fragment of a large crocodile from the La Meseta Formation. • Skeletal elements of large phororhacoid (large land bird), which attained a height of approximately 2 meters, were found. The occurrence of this land bird, together with the crocodile remains, provides additional evidence of a continuous land connection between southern South America during the early Tertiary. • Stratigraphic study of the KIT shallow-water sequence on Seymour Island is unique, because deposition across the sequence was continuous, whereas other shallow-water K/T sections are characterized either by a hiatus or a condensed section. • Preliminary analysis of the macrofossil fauna across the K/T boundary indicates that in contrast to other K/T boundary sections, there is no abrupt change in the marine benthic fauna but rather a gradual transition over approximately 40 meters of section which includes the boundary.
• A number of ammonites were collected above the KIT boundary as defined by dinocysts. This apparent diachroneity of the KIT boundary between different groups of marine organisms highlights the problem of no formalized definition of the KIT boundary and illustrates the problem of defining the KIT boundary in a section where there was continuous deposition. This research was supported by National Science Foundation grant DPP 84-16783.
New fossil vertebrates from Seymour Island, Antarctic Peninsula MICHAEL 0. WOODBURNE and JUDD A. CASE, Department of Earth Sciences University of California Riverside, California 92521
DAN S. CHANEY U.S. National Museum Smithsonian institution Washington, D.C. 20560
The 1986-1987 field season on Seymour Island (figure 1) yielded new remains of an extinct whale, a large flightless
SOBRAL FM
H1
RV-82001
SEYMOUR IS.
A.
I
L/ MESETA + + FM.
/ RV-8405 CROSS VALLEY FM
LOPEZ de BE RTODANO FORMATION SOBR NNNNNNNNN FM
I I I I I 0 I 2 3 4 5 K
Figure 1. Map of Seymour Island and the Antarctic Peninsula region. The La Meseta Formation is of late Eocene age. All other rock units are older (Late Cretaceous to Paleocene). Fossil localities produced marsupials, crocodiles, and plants (RV-8200) and the phororhacoid bird (RV-8405). The whale site is just below the "F" in La Meseta Formation. ("Km" denotes "kilometer?' "Fm?' denotes "formation.")
References Zinsmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S. 17(5), 63-64. Zinsmeister, W.J. 1985. 1985 Seymour Island Expedition. Antarctic Journal of the U.S. 19(5), 41-42.
terrestrial bird, the first postcranial skeleton of a penguin-like bird, and a lower mandible of a small crocodilian. All of the fossils were recovered from the La Meseta Formation of late Eocene age (approximately 40 million years old). The whale material comprises part of the skull and the vertebrae and ribs of much of the thoracic region. The material is well preserved and shows that it pertains to a basiliosaurine, a member of the archaeocete (ancient-toothed whale) group. According to Ewan Fordyce, University of Otago, New Zealand, who collected the specimens, these remains constitute the best documentation of this kind of whale in the Southern Hemisphere. The animal, which apparently lived in shallow marine waters, may have been about 10 meters long. The specimens are now under study by Fordyce. A wide variety of nominally marine penguin-type birds has been recovered in this and past seasons from Seymour Island. The partial postcranial skeleton recovered this time will enhance functional comparisons between these ancient birds and their modern counterparts. A large (about 2 meters tall), predaceous terrestrial (flightless) bird that apparently pertains to the phororhacoid group lived on Seymour Island in the late Eocene, as shown by a portion of its beak recovered this season (Case, Woodburne, and Chaney in press-a). The group is also known from South America, from the Oligocene to the present (Marshall 1978). Although modern representatives are about the size of a road-runner, the ancient birds were of large size and apparently filled the ecological niche of a large carnivore in the Eocene and Oligocene. Although the legs were relatively slender, the body and head were massive, as shown in reconstructions based on South American fossils (figure 2). The Seymour Island material pre-dates the known age of the group in South America, and some of the bird footprints reported from yet earlier Eocene (approximately 46 million years ago) rocks on King George Island (Covacevich and Rich 1982; Watts 1982) may pertain to this group, as well. In any case, the presence of such derived birds in the american and antarctic Southern Hemisphere indicates that their ancestors must have inhabited this region well before the time the fossils reported here were preserved. Furthermore, the flightless nature of these birds requires a solid overland pathway by which they dispersed between South America and peninsular Antarctica. This strengthens the proposals made earlier (Woodburne and Zinsmeister 1984; Case, Woodburne, and Chaney in press-b) for the existence of such a land connection, based on the presence in La Meseta rocks of two kinds of marsupials and Not hofagus (southern beech) plants. The presence in these same deposits of small crocodiles is consistent with this proposal, ANTARCTIC JOURNAL
