Feldmann, R.M., and W.J. Zinsmeister. 1984. Fossil crabs (Decapoda: Brachyura) from the La Meseta Formation (Eocene) of Antarctica: Paleoecological and biogeographic implications. Journal of Paleon- tology, 58(4), 1046-1061. Macellari, C.E. 1986. Late Campanian-Maastrichtian ammonite fauna from Seymour Island (Antarctic Peninsula). Journal of Paleontology, Vol. 60, (The Paleontological Society Memoir 18, Part 2.) Sadler, P.M. In press. Geometry and stratification of Paleogene and latest Cretaceous units on Seymour Island, northern Antarctic Penin- -j sula. In R.M. Feldmann and M.O. Woodburne, (Eds.), Geology and paleontology of Seymour island, Antarctica. (Geological Society of Amer- ica Memoir 169.) Tshudy, D., and R.M. Feldmann. In press. Macrurous decapod crusta- ceans, and their epibionts, from the Lopez de Bertodano Formation (Late Cretaceous), Seymour Island, Antarctica. In R.M. Feldmann and M . O. Woodburne, (Eds.), Geology and paleontology of Seymour Island, Antarctica. (Geological Society of America Memoir 169.)

Figure 2. Hoploparia stokesi Weller. Latex cast of a specimen from the Lopez de Bertodano Formation, preserved as a molted, but complete, carapace and abdomen. (Bar scale equals 1 centimeter.)

Palynological investigations of the cysts, acritarchs) palynomorphs and documentation of their distribution patterns. The dinocyst assemblages have proved James Ross Island basin, Antarctica particularly useful for biostratigraphy (Askin in press), and the land plant-derived spores and pollen should add useful infor- mation on climatic evolution of the area. Unlike terrestrial sedi- ROSEMARY A. ASKIN ments, which can contain palynomorphs of relatively local deri- vation, the mainly nearshore marine sediments of Seymour Island contain spores and pollen transported from a wide range Department of Earth Sciences University of California of terrestrial habitats and microclimates. Thus these as- Riverside, California 92521

During December 1986 and January 1987, additional sam- Vega Island AAfarctica pling of Campanian to Eocene sediments was carried out for palynological study in the James Ross Island basin (figure), northeastern Antarctic Peninsula. The 300 samples collected are Naze (J mainly from Seymour Island and cover certain intervals of 640 interest in more detail than was previously available. Data from c::; Island these samples will refine and extend the palynomorph zonation 9 5 10 15 20 Km proposed for the upper Campanian to Paleocene part of the VUIO succession (Askin in press). Parts of the upper Lopez de Ber- I) Point todano Formation, including the glauconitic interval that spans I Cockburn James Ross Island ( the Cretaceous/Tertiary boundary, and parts of the Eocene La Island Meseta Formation were sampled. Short helicopter-supported visits also were made to three Hamilton nearby islands to collect from ?Campanian sections. The three Seymour sampled localities are Cockburn Island, Humps Island, and Ula Island Point on eastern James Ross Island (figure). Fossil palynomorphs are ubiquitous in the Seymour and nearby island sedimentary succession and occur, often abun- EPateogene sediments Snow Hill Island dantly, in all 935 samples processed to date. It is expected that Cretaceous sediments the newly collected samples also will be productive, bringing [] the samples available for this study to a total of over 1,200. The present phase of this project includes taxonomic descrip- Locality map for the James Ross Island basin. ("Km" denotes tion of nonmarine (spores, pollen) and marine (dinoflagellate "kilometer?")

1987 REVIEW 13 semblages will provide a broad view of the prevailing pal- answer such questions, by providing inferred data on proximity eoclimatic conditions. to shoreline, higher vs. lower energy environments, and so on. The Cretaceous cryptogam (ferns and lower plants) spores of I thank F.C. Barbis and T.R. Kelley for 1986-1987 collection of Seymour Island (Askin in preparation) include an overwhelm- samples, and the Captain and crew of USCGC Glacier for logistic ing abundance of Stereisporites antiquasporites and support. This research is supported by National Science Foun- Laevigatosporites ovatus. These two species, plus fewer numbers dation grant DPP 83-14186. of S. regiuln, usually total over 75 percent of the spore compo- nent. The abundance of Stereisporites (the spores of Sphagnum References moss), along with some Azolla sp. (water fern), suggests moist conditions with ample standing water, consistent with humid Askin, R. A. In press. Campanian to Paleocene palynological succession temperate paleoclimates indicated both by the palynomorph of Seymour and adjacent islands, northeastern Antarctic Peninsula. Geology and paleon- assemblages (dominated by podocarpaceous conifer pollen) In R.M. Feldmann and M.O. Woodburne (Eds.), tology of Seymour Island, Antarctic Peninsula. (Geological Society of and by other lines of evidence (e.g., fossil wood; Francis 1986). America Memoir 169.) Alternatively, hydrodynamic properties of the small Ste- Askin, R.A. In preparation. Cryptogam spores from the upper Campa- reisporites and Laevigatosporites spores may have contributed to nian and Maastrichtian of Seymour Island, Antarctica. their concentration. Analysis of all the acid-insoluble organic Francis, J.E. 1986. Growth rings in Cretaceous and Tertiary wood from components of the sediments (palynomorphs, plus cuticle, Antarctica and their palaeoclimatic implications. Palaeontology, 29, amorphous and algal matter, and woody debris) should help 665-686.

profiles from the planktonic forams in the oceans surrounding A study of the internal annual growth Antarctica (Kennett 1977) show that the sea-surface tem- lines of the Late Eocene mollusk peratures in the southern oceans during the Late Eocene were not significantly different from the sea-surface temperatures off Eurhomalea antarctica the coast of Chile today. It is believed that the difference in patterns is due to low levels of plankton productivity in the winter months at the high lati- BRENDA L. DEXTRAZE and WILLIAM J. ZINSMEISTER tudes when the daily levels of sunlight are not high enough to maintain significant photosynthetic levels. In a recent study, Department of Earth and Atmospheric Sciences Tilzer and Dubinsky (1987) found that respiration rates in phy- Purdue University toplankton are temperature-dependent, with respiration rates West Lafayette, Indiana 47907 decreasing with temperature. Plants lose carbon during respira- tion so the mass balance of the population is controlled by the During the last decade, much work has been done using the respiration rate. The phytoplankton are therefore able to main- internal growth increments annually recorded in bivalve shells. tain a positive mass balance during the long antarctic winter These growth increments are believed to record the slowing because they are able to conserve carbon and stored energy at down or cessation of growth of the bivalve during the cold such low temperatures. If the temperature was raised even a winter months (Panella and MacClintock 1968). These growth few degrees, then the respiration rates increased enough that it lines are analogous to tree rings and are very useful environ- was impossible for the phytoplankton to maintain this positive mental indicators. They record the ambient seawater tem- mass balance. peratures (Urey et al. 1951) as well as the geochemical history of During the Late Eocene, the average surface seawater tem- the seawater in which the bivalve lived (Eisma, Mook, and Das peratures in the southern oceans were approximately 9° to 12°C 1976). In this study, the internal annual growth lines of two Late higher than they are today (Kennett 1977). According to Tilzer Eocene antarctic mollusks (Eurhomalea antarctica and E. newtoni) and Dubinsky (1987), the phytoplankton population would from Seymour Island (64.5°S) were compared to the growth have been greatly reduced during the winter months. There- lines from a Recent Eurhomalea species (E. lenticularis) from two South American localities, Chile at 34.5°S and Patagonia at 55°S. No significant difference can be seen between the growth increment patterns of the Chilean and Patagonian specimens. These individuals of Eurhomalea show a long period of growth broken by thin annual increments. It is believed that this pattern reflects fast growth during most of the year and slow growth during the winter months (figure). Eocene shells from Seymour Island show a different type of growth increment pattern: an extremely short period of growth followed by a thick winter line. In most cases, temperature regime is considered to be the primary cause of growth increment patterns in bivalves. In this case it does not appear that the temperature regime dictated the growth increment patterns. This is because O temperature Thin section of Eurhomalea lenticularis from central Chile, 34.5°S.

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