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The evolution of permafrost on the Kara shelf is reconstructed for the past 125 kyr. The work includes zoning of the shelf according to geological history; compiling sea level and ground temperature scenarios within the distinguished zones; and modeling to evaluate the thickness of permafrost and the distribution of frozen, cooled and thawed deposits. Special attention is given to the scenarios of the evolution of ground temperature in key stages of history that determined the current state of the Kara shelf permafrost zone: characterization of the extensiveness and duration of the existence of the sea during stage 3 of the marine oxygen isotope stratigraphy (MIS-3), the spread of glaciation and dammed basins in MIS-2. The present shelf is divided into areas of continuous, discontinuous-to-sporadic and sporadic permafrost. Cooled deposits occur at the western and northwestern water zones and correspond to areas of MIS-2 glaciation. Permafrost occurs in the periglacial domain that is within a zone of modern sea depth from 0 to 100 m, adjacent to the continent. The distribution of permafrost is mostly sporadic in the southwest of this zone, while it is mostly continuous in the northeast. The thickness of permafrost does not exceed 100 m in the southeast and ranges from 100 to 300 m in the northeast. Thawed deposits are confined to the estuaries of large rivers and the deepwater part of the St. Anna trench. The modeling results are correlated to the available field data and are presented as a geocryological map. The formation of frozen, cooled and thawed deposits of the region is inferred to depend on the spread of ice sheets, sea level, and duration of shelf freezing and thawing periods.

Mineral deposits in the Neoarchean greenstone belts in the Fennoscandian Shield, especially in its eastern (Russian) part, are not as numerous as in Archean belts of Canada, Australia, or Southern Africa. The goal of the present paper is to show with an example of Tiksheozersky belt, that Neoarchean greenstone belts in Northern Karelia and Kola Peninsula do contain ore occurrences, typical to greenstone belts in the world, therefore prospects of these geological structures for mineral deposits are not uncovered fully. Ore occurrences of jaspilite, massive sulfide pirrhotite ore, molybdenite with uranium and graphite, arsenopyrite, and gold were found in the Kichany structure of the Tiksheozersky belt. Jaspilites and massive sulfide ores were considered as syngenetic to volcanic-sedimentary host rocks. Occurrences of molybdenite, arsenopyrite, and gold are epigenetic, controlled by zones of alteration. Zonality in ore-bearing altered rocks, peculiar properties of their chemical and mineral composition, as well as composition of rock-forming and ore minerals, were studied in detail. Age of processes of alteration was estimated with different geochronological methods. Dating of zircon grains from the molybdenite occurrence with LA-ICP-MS method showed two events 2600-2700 Ma (formation of host rocks) and 2100-1900 Ma (regional metamorphism) in their formation. Estimation of age of quartz-garnet-tourmaline metasomatite from arsenopyrite occurrence with composition of monazite gave 1789 ± 47 Ma, it corresponds to post-metamorphic event, probably connected with intrusions of tourmaline granites. Gold mineralization in quartz metasomatite and skarnoid has near the same age: titanite, which contains inclusions of gold, formed 1739 ± 15 Ma ago. Hence, occurrences of gold, arsenopyrite, and molybdenite formed in Neoarchean rocks during Palaeproterozoic (Svecofennian) metamorphic-metasomatic events. Gold mineralization is the most promising in the belt. Position of gold occurrences is controlled by thrust zones, gold concentrates in altered amphibolite with arsenopyrite-pirrhotite mineralization.

Mantis shrimp commonly inhabit seafloor environments with an abundance of visual features including conspecifics, predators, prey and landmarks used for navigation. Although these animals are capable of discriminating color and polarization, it is unknown what specific attributes of a visual object are important during recognition. Here, we show that mantis shrimp of the species Neogonodactylus oerstedii are able to learn the shape of a trained target. Further, when the shape and color of a target that they had been trained to identify were placed in conflict, N. oerstedii tended to choose the target of the trained shape over the target of the trained color. Thus, we conclude that the shape of the target was more salient than its color during recognition by N. oerstedii, suggesting that the shapes of objects, such as landmarks or other animals, are important for their identification by the species., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2021. Published by The Company of Biologists Ltd.)