The paper deals with Recent and relic phosphatic soils of ornithogenic origin which occur in ice free oasis of the maritime Antarctic Zone (Antarctic Peninsula and King George Island regions). These soils form on rocky and clay weathering covers within and around of penguin rookeries. Their morphology strongly depends on penological character of a substrate and climatic differentiation of a region. They are built of a surface layer of guano and underlying zone of a phosphatized rock. Except organic matter and unstable urates, the guano contains calcium phosphates (fluorapatite somtimes brushite) and magnesium-amonium phosphate (struvite). The phosphatized zone consists of phosphatic- silicate clays in which occur diversified aluminium-iron phosphates bearing potassium and ammonium ions (leucophosphite, minyulite, taranakite, amorphous aluminium phosphate). The guano layer is strongly reduced by erosion and weathering in ornithogenic relic soils left by penguins in areas abandoned by them during Holocene. Formation of a humus horizon of a plant origin may be observed under a vegetation cover in the relic soils. Clays of the phosphatized zone in these areas are transformed in the processes of chemical and mechanical weathering, by mass movements and frost processes.
A high content of fluorine was found in ornithogenic soils around penguin rookeries on King George Island. South Shetland Islands. Fluorine is inherent in 0.11% in krill (Euphausia superba). eaten by penguins. Fluorine content in penguins excreta increased approximately to 0.43%. and after decomposition and leaching to 1.03%. The concentration grew during mineralization of organic matter in guano (up to 2.2%). In a surface layer of guano fluorine occurred in apatite. A phosphatization was noted in a subsurface zone as the result of a reaction between guano leachates and weathered volcanic rocks. In the upper part of this zone near the large rookeries a fluorine occurred in minyulite (aluminium phosphate containing potassium and fluorine) and fluorine content here reached 3.5%. Sometimes fluorine was also bound with amorphous aluminium phosphate (up. to 2.0%). formed as a result of incongruently dissolving of minyulite in pure water.
The results of several years of studies concerning the role of penguin rookeries in the functioning of the land ecosystems in the maritime Antarctic are summarized. The origins of phosphatic ornithogenic soil in the areas of currently active penguin rookeries arc presented. In the maritime Antarctic occurs relatively fast microbiological decomposition and mineralization of large amounts of excrements carried into coastal area by penguins during breeding period. Chemically aggressive water solutions of guano react with underlaying rocks. This process brings about the occurrence of wide zones of phosphatization. These processes cause the appearance of the series of phosphate minerals whose composition and properties depend on the changing physical and chemical conditions of the soil environment. It has been discovered that in the rookeries for various reasons abandoned by penguins phosphates are still present in large amounts and, gradually changed and washed out, have been for hundreds, or even thousands years a source of nutrients for plants growing in poor Antarctic land ecosystems. These soils came to be called the relic ornithogenic soils of the maritime Antarctic. The stages of plant colonization in the abandoned penguin rookeries were traced. The differences in the fate of the organic matter carried out from the sea to the coastal area by sea-birds in various climatic zones were discussed.
Przedstawiono wykaz nowych nazw geograficznych wprowadzonych na obszarze Wyspy Seymour (Marambio), Półwysep Antarktyczny (fig. 1, pl. 1—2) w czasie prac terenowych argentyńsko-polskiej grupy geologicznej w sezonie 1993-1994.
At the turn of October 1985, the abundance of breeding Adelie penguins was estimated at the Hope Bay oasis on the Antarctic Peninsula and on Seymour Island. In the Hope Bay rookery, 123850 pairs of penguins were recorded, beginning their breeding at the end of October. Data so far obtained indicate a continuous increase in the number of birds sat this rookery. On the other hand, the Seymour Island colony consisted of 21954 pairs of Adélie penguins. Clear differences in the geomorphological structure of areas occupied by penguins in those two places are discussed. No gentoo penguins were detected in either of the colonies.
A sequence of glacial deposits up to 4 m thick unconformably overlies the Eocene La Meseta Formation on the Seymour Island plateau (meseta) and forms a lithostratigraphically distinct unit in the succession of the James Ross Basin, which is formally named here as the Weddell Sea Formation. The formation is thus far known only from Seymour Island. This is a terrestrial melt-out till which contains abundant erratics and also reworked Cretaceous–Tertiary micro- and macrofossils within a silty clay matrix. The terrestrial origin of this till is shown by glacial striations at the base of the unit. The largest erratics (up to 3 m in diameter) are composed of plutonic (granitoids) and metamorphic (gneiss and crystalline schist) rocks of the Antarctic Peninsula provenance. Smaller in size and much more numerous are erratics of volcanic rocks, represented by andesite, basalt and corresponding pyroclastics of the James Ross Island Volcanic Group. Less common are erratics of sedimentary rocks, sometimes bearing fossils derived from the underlying Tertiary and Cretaceous strata. A few erratics from the top of the studied sequence are conglomerates of the Cockburn Island Formation with a foraminifer fauna. These are the youngest clasts within the Weddell Sea Formation. The presence of the Pliocene index fossil Ammoelphidiella antarctica Conato et Segre, 1974 indicates a lower age limit of latest Pliocene or earliest Pleistocene age. The upper age limit of the formation has not been established. An encrusting, unilamellar, colony of the bryozoan Escharella Gray, 1848 has been found on the one of erratics from the Weddell Sea Formation. This is the first fossil record of this genus in Antarctica.
One of the most significant global climatic events in the Cenozoic was the transition from greenhouse to icehouse conditions in Antarctica. Tectonic evolution of the region and gradual cooling at the end of Eocene led to the first appearance of ice sheets at the Eocene/Oligocene boundary (ca. 34 Ma). Here we report geological record of mountain glaciers that preceded major ice sheet formation in Antarctica. A terrestrial, valley-type tillite up to 65 metres thick was revealed between two basaltic lava sequences in the Eocene– Oligocene Point Thomas Formation at Hervé Cove – Breccia Crag in Admiralty Bay, King George Island, South Shetland Islands. K-Ar dating of the lavas suggests the age of the glaciation at 45–41 Ma (Middle Eocene). It is the oldest Cenozoic record of alpine glaciers in West Antarctica, providing insight into the onset of glaciation of the Antarctic Peninsula and South Shetland Islands.
Fossil bird remains assignable to ratites (palaeognathous birds) are described from the Paleogene strata of the La Meseta Formation of Seymour Island, Antarctic Peninsula. This record sheds new light on Gondwana's avian history.
Mineral composition of bedrock is the main factor determining salt mineralization in the weathering zone of Seymour (Marambio) Island (maritime — Antarctic continent climatic boundary). Supply of salts by sea water spray can accelerate weathering process, modify chemical formula of salt minerals and give ephemeral efflorescences of easy soluble chlorides and partially longer lasting gypsum on the surface. Microbiologically mediated oxidation of sulphides and followed acid sulphate drainage formed K and Na jarosite, basic amorphous aluminium sulphate, gypsum, aluminium bearing ferrihydrite and ankerite in weathering zone of Paleogene sediments. Intense alteration of well-lithified, calcareous sandstones of unit 1 of the López de Bertodano Formation (Cretaceous) on old erosion surface led localy to surface mineralization comparable with that found in Antarctic Continent. Stones laying on the soil surface are covered by thin red film of ferrihydrite above the soil level and by light green crust of aragonite coloured by glauconite pigment on the underground side. Most of the Cretaceous sediment does not contain sulphides nor alteration susceptible silicates thus ephemeral sea salts efflorescences observed on its surface are more prominent than in another places.
Eocene penguin remains from Seymour Island (Antarctica) are so far the oldest−known record of extinct Sphenisciformes. Rich Argentineand Polish collections of penguin bones from the La Meseta Formation are taxonomically revised on tarsometatarsal morphology. Two genera and four species are erected: Mesetaornis polarisgen. et sp. n., Marambiornis exilisgen. et sp. n., Delphinornis arctowskiisp. n. and D. gracilissp. n. Moreover, the diagnoses of already described species: Anthropornis nordenskjoeldi, A. grandis, Palaeeudyptes klekowskii, P. gunnari, Archaeospheniscus wimani and Delphinornis larseniare revised as well. Gradual cooling of climate, changes of environment andtrophic relationships, that lasted several millions years, were most probably responsible forthe intense speciation and taxonomic diversification of the Middle–Late Eocene La Meseta penguins.
The Panorama Point Beds represent a subfacies of the Early to Middle Permian Radok Conglomerate, which is the oldest known sedimentary unit in the Prince Charles Mountains, MacRobertson Land, East Antarctica. This unit records clastic sedimentation in fresh−water depositional system during the early stages of development of the Lambert Graben, a major structural valley surrounded by crystalline highlands in the southern part of Gondwana. It contains common siderite precipitated through early diagenetic processes in the swamp, stagnant water, and stream−flow environments. There are two types of siderite in the Panorama Point Beds: (1) disseminated cement that occurs throughout the sedimentary suc− cession; and (2) concretions that occur at recurrent horizons in fine−grained sediments. The cement is composed of Fe−depleted siderite (less than 90mol%FeCO3)with an elevated con− tent of magnesium, and trace and rare earth elements. It has negative #2;13CVPDB values (−4.5 to −1.5‰). The concretions are dominated by Fe−rich siderite (more than 90mol% FeCO3),with positive 13CVPDB values (+1 to +8‰). There are no noticeable differences in the oxygen (18OVPDB between −20 and −15‰) and strontium (87Sr/86Sr between 0.7271 and 0.7281) iso− topic compositions between the siderite types. The cement and concretions developed in the nearsurface to subsurface environment dominated by suboxic and anoxic methanic degrada− tion of organic matter, respectively. The common presence of siderite in the Panorama Point Beds suggests that fresh−water environments of the Lambert Graben were covered by vegetation, starting from the early history of its development in the Early Permian.