Skamieniałości górnej kredy i trzeciorzędu z osadów talasoglacjalnych na Półwyspie Melville'a, Wyspa Króla Jerzego (Zachodnia Antarktyka)

Andrzej Gaździcki, Ryszard Wrona



Numerous well-preserved fossils have been found at the Melville Peninsula by the Polish Antarctic Expedition of the Polish Academy of Sciences in the austral summer 1980/81. The fossils come from a sequence of thin-bedded sandy-marly glaciomarine sediments about 200 m thick. The deposits also yield erratic boulders (dropstones) coming from the Antarctic continent. Specific lithological and paleontological features of these deposits made it possible to propose a new lithostratigraphic unit for West Antarctica - the Cape Melville Forniation (3). Marine microfossils recorded in the formation include planktonic assemblage of coccoliths: Corollithion achylosum (Stover), C. exiguum Stradner, Hayesites albiensis Manivit, Tetralithus gothicus Deflandre, Prediscosphaera cretacea (Arkhangęlsky), Vekshinella and Zygodiscus as well as diatoms (Coscinodiscus), chrysomonad cysts, silicoflagellates (Distephanus) and agglutinated and calcareous benthic foraminifera (Cyclammina, Pullenia and Uvigerina) (Figs. 4-5). Marine invertebrates are here represented by solitary, corals (Flabellum), bryozoans, bivalves (? Portlandia), gastropods (? Fusus), scaphopods, belemnites, polychaetes (Glycera, Ophryotrocha), ostracods, crabs (Majidae), asteroids and echinoids (? Isechinus and cidaroids) (Figs. 6-8), and marine vertebrates - by innumerous fish remains. Deposits yielding these fossils are strongly bioturbated. A marked predominance of benthic organisms and numerous traces of their life activities (Fig. 3) and occurrence of very numerous coprolites suggest sedimentation in a low-energy environment of shallow-shelf zone. The presence of erratic boulders in rocks of the Cape Melville Formation evidences continental glaciation (Melville Glaciation - 3). The boulders are usually about 50 cm in size but some of them approach 2 m in size (Figs. 2, 9). Limestone boulders were found to yield numerous well-preserved Cambrian fossils: algae (Epiphyton), archaeocyathids, brachiopods, monoplacophorans, gastropods, hyolithids, trilobites, ostracods and numerous enigmatic microfossils (Anabaritidae, Chancelloriidae) (Figs. 10-11). Cambrias rocks similar in lithology and fossil content are known from the Ellsworth Mts (14, 15), Pensacola Mts (1.2) and Transantarctic Mts (10, 11, 8, 9, 13) in Antarctica.
Of the rich fossil assemblage recorded in rocks of the Cape Melville Formation (3), coccoliths primarily indicate its Upper Cretaceous age (see above). Some groups of organisms, especially silicoflagellates, diatoms, foraminifera, corals and bivalves, comprise forms also known from the Tertiary. That is why it is difficult to precise the age of glaciomarine sedimentary sequence from the Melville Peninsula and, therefore, the time of Melville Glaciation. It may be only supposed that sedimentation of the formation and glaciation were taking place in the Late Cretaceous and/or Tertiary.

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