ИСТИНА

Soils inside the rocks develop under the influence of endolithic communities occupying structural cavities in the interior of solid rocks. Scientific rationale for endolithic organisms was provided by Friedmann (1982) revealing that bacteria, algae, fungi and specific lichens find their ecological niche within few upper centimeters of the rocks, thus escaping in hot/cold deserts and high mountains the intensive UV-radiation, moisture deficit and wind abrasion. The most suitable rocks for endolithic colonization are sandstones, various granitoids, marbles and any others with a significant content of translucent and/or transparent mineral grains which make the primary organic matter production possible inside the rock (dark basalts are more subjected to epilithic colonization). Our studies in East Antarctica oases show that the system “endolithic organisms – parent rock” has all characteristic features of soils: (1) the rock (parent material) layer subjected to the action of external abiogenic factors, (2) the living organisms functioning in this rock and synthesizing/decomposing organic matter, (3) the in situ transformation of initial rock under the impact of abiogenic and biogenic factors with accumulation and removal of the transformation products and development of the vertical heterogeneity composing the microprofile. It is very important that endolithic pedogenesis is capable to produce autochthonous fine earth. The other crucial feature related to pedogenesis is the presence of organomineral horizon – the hotspot of biota-rock interactions. Microtomography data shows that different layers of endolithic system are connected with the fissure network which serve as the transport system for elements migration. Our measurements in Larsemann Hills oasis (East Antarctica) indicate that the carbon content in endolithic organomineral horizons developed in granitoid rocks varies from 0.2 to 3.7%, the nitrogen content - from 0.02 to 0.47%, and the mean residence time of organic matter reaches 480 ± 25 yrs. The values of δ13C obtained for the dated samples attest to a somewhat heavier isotopic composition (-21.0 to -23.7 ‰) of the organic matter in comparison with the values typical of C3 plants, as well as with the values obtained for the endolithic material from the Dry Valleys of Antarctica (Hopkins et al., 2009). Our preliminary estimate of average endolithically generated organic C stocks in granites of Larsemann oasis in East Antarctica is 0.037±0.019 g C/сm2. The major products of the endolithic pedogenesis are the silty–sandy fine earth and abundant amorphous Fe–Al–Si–C-containing films with admixtures of K, Na, Mg, Ca, S that are formed on the walls of the fissures inside the rocks and on the lower face of exfoliation plates; precipitation of these film is specified by the mechanical and oxidation geochemical barriers at the air/rock interface. The study of endolithic weathering front with the approaches of soil science needs more systematization and understanding of the place these objects occupy in the soils world. It can turn out that endolithic soils are the most spatially abundant soil bodies in extreme environment of Antarctica, some highlands and deserts. Besides such objects should be recognized as an early-Earth “protosoils”. The data on major features of endolithic soils studied by contemporary microtomography, SEM/TEM and isotopic techniques will be discussed in the presentation.