Krzysztof P. Krajewski

Dolerites of Svalbard, north-west Barents Sea Shelf: age, tectonic setting and significance for geotectonic interpretation of the High-Arctic Large Igneous Province

The dolerites of Svalbard are mineralogically and geochemically homogeneous with geochemical features typical of continental within-plate tholeiites. Their geochemistry is similar to tholeiites belonging to a bimodal suite defined as the High-Arctic Large Igneous Province (HALIP). K–Ar dating of numerous dolerites sampled from many locations across Svalbard define a narrow time span of this magmatism from 125.5±3.6 to 78.3±2.6 Mya. Discrete peaks of intensive activity occurred at 115.3, 100.8, 91.3 and 78.5 Mya corresponding to (1) breakup of the continental crust and formation of an initial rift as a result of mantle plume activity, located in the southern part of the Alpha Ridge; (2) magmatic activity related to spreading along the Alpha Ridge that led to the development of the initial oceanic crust and (3) continuation of spreading along the Alpha Ridge and termination of magmatic activity related to HALIP (last two peaks at 91.3 and 78.5 Mya).

The first record of fossil penguins from East Antarctica

Abstract This paper presents the first fossil penguin from East Antarctica, and the only one known south of the Antarctic Circle. It is represented by two well-preserved elements of the wing skeleton, humerus and radius, obviously assignable to the extant genus Spheniscus. They were found in the glaciomarine succession of the Fisher Bench Formation (Fisher Massif, Prince Charles Mountains, Mac. Robertson Land), which was dated using Strontium Isotope Stratigraphy to be Late Miocene in age (10.2 Ma). They are only slightly younger than the oldest remains undoubtedly attributable to this taxon. The X-ray diffraction and Fourier Transform Infrared Spectroscopy indicate diagenetic alteration of the original bone bioapatite under dominantly marine conditions. The Late Miocene was a period of ice margin retreat and marine incursion into the Lambert embayment that followed Middle Miocene cooling of the Antarctic climate. The fossils strongly suggest that variable climatic and environmental conditions in East Antarctica may have been an important factor in the evolution of penguins there during the Neogene.

Remnants of Antarctic vegetation on King George Island during the early Miocene Melville Glaciation

Palynological analyses of 12 samples from the Cape Melville Formation, which crops out on easternmost King George Island, Antarctica, provide new information on the type of vegetation that covered the South Shetland Islands during the early Miocene Melville Glaciation, c. 23–21 Ma. The assemblage recovered was mostly characterised by in situ algae such as leiospheres along with acanthomorph acritarchs, both glacial indicators. The sparse in situ terrestrial palynomorph assemblage included tundra-indicative moss spores Coptospora sp., rare podocarp conifer and various angiosperm pollen. The latter includes pollen of several species of Nothofagidites, plus rare Asteraceae, Caryophyllaceae (Colobanthus-type) and Chenopodipollis. The majority of the palynomorphs recovered are interpreted as reworked, denoting glacial scouring and redeposition from various sites in the Antarctic Peninsula and the South Shetland Islands. These reworked palynomorphs are of Permian to Paleogene age. This reworked component provides insight into the potential sources of reworking, and is consistent with multiple cycles of glacial advances to the Melville Peninsula at the time of deposition. The penecontemporaneous palynomorphs recovered provide new data on the climatic regime and glacial intensification during the early Miocene on King George Island.

Terrestrial and marine floral response to latest Eocene and Oligocene events on the Antarctic Peninsula

abstract Palynological results from opposite sides of the northernmost Antarctic Peninsula provide insight on terrestrial vegetation and sea-surface conditions immediately before the Eocene–Oligocene transition (EOT), through Early Oligocene glacial conditions and the subsequent Late Oligocene interglacial interval. A latest Eocene sample set from the uppermost La Meseta Formation on Seymour Island, James Ross (back-arc) Basin, records a low-diversity Nothofagus (southern beech)-dominated vegetation with some podocarp conifers similar to Valdivian-type forest found today in Chile and Argentina. Marine organicwalled phytoplankton include leiospheres and Eocene dinoflagellate cysts such as Vozzhennikovia rotunda, V. apertura, Senegalinium asymmetricum and Spinidinium macmurdoense. Immediately before the EOT near the top of the section the decrease in terrestrial palynomorphs, increase in reworked specimens, disappearance of key dinocysts, and overwhelming numbers of sea-ice-indicative leiospheres plus the small dinoflagellate cyst Impletosphaeridium signal the onset of glacial conditions in a subpolar climate. Early to Late Oligocene samples from the Polonez Cove and Boy Point formations on King George Island, South Shetland Islands (magmatic arc), yielded an extremely depauperate terrestrial flora, likely resulting in part from poor vegetation cover during the Polonez Glaciation but also because of destruction of vegetation due to continued regional volcanism. The prevalence of sea-ice-indicative leiospheres in the marine palynomorph component is consistent with polar to subpolar conditions during and following the Polonez Glaciation.