Palynoassemblages from a Theropod Dinosaur site in the Snow Hill Island Formation (Maastrichtian) at The Naze, James Ross Island, Antarctic Peninsula.

DI PASQUO, M.M., MARTIN, J.E.,

Tennessee

Simposio; AASP 42nd Annual Meeting; 2009

The Palynological Society

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-no-proof:yes;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> This contribution aims to characterize and give the age of the palynoassemblages associated with a dinosaur found on the The Naze, a peninsula on the northern margin of James Ross Island, Antarctica. The 90-m-thick section of the Cape Lamb Member, Snow Hill Island Formation, begins at sea level, ends below a basalt sill, and is composed of interbedded green-grey massive and laminated fine-grained sandstones and mudstones. Fourteen samples contained palynomorphs, yielding moderately diverse assemblages with a total of 100 relatively well-preserved species. The principal terrestrial groups are represented by lycophytes (6 species), pteridophytes (12 species), gymnosperms (13 species) and angiosperms (10 species). Aquatic palynomorphs belong to chlorococcaleans (8 species), dinoflagellates (49 species) and the acritarch Michrystridium piliferum. Some trilete spores (Perotrilites majus), pollen grains (Podocarpidites, Nothofagidites), dinoflagellates (Isabelidinium cretaceum- gravidum, Operculodinium radiculatum, Spiniferites ramosus complex, Xenascus plotei) and chlorococcaleans (Nummus monoculatus) are always present. Instead, M.  piliferum and other dinoflagellates (e.g., Batiacasphaera grandis, Canninginopsis ordospinosa, Manumiella spp., Trichodinium castaneum-T. chilensis complex) show quantitative variations possibly related to sea-level fluctuations and/or nutrient availability within an inner platform with contributions from the littoral/inland environments. Although assemblages show no major shifts within the section, the appearance of Paleocystodinium pilosum and the disappearance of Odontochitina porifera at ca. 20m from the base and the appearance of Manumiella seelandica, Alterbidinium acutulum and T. castaneum-chilensis complex at ca. 25m and Spinidium essoi at ca. 35m indicate the early-late Maastrichtian boundary within this interval, which is reinforced by comparison with other similar assemblages from the Southern Ocean.