Sedimentary Rocks in the Basement of the Alpha-Mendeleev Rise, Arctic Ocean

The results of petrographic, petrogeochemical and isotopic studies of sedimentary rocks obtained from bedrock outcrops of the Alpha-Mendeleev Rise, Arctic Ocean, using manipulators of a submarine research vessel (SRV) of the Russian Ministry of Defense during two expeditions conducted in 2014 and 2016 are considered and discussed in the article. Three sequences are identified in the basement of this Rise. The lower sequence (O-3-S-2) is composed of pure dolomite rocks (hereafter, dolomites proper), as well as dolomites with the terrigenous and bioclastic admixture, limestones with the terrigenous and bioclastic admixture, and quartz sandstones. They were formed in the coastal and shallow shelf environments of the tropical sea associated with carbonate platforms adjacent to river discharge areas. The middle sequence (D-2-D-3) is composed of limestones with the terrigenous and bioclastic admixture, as well as quartz-feldspar sandstones, which originated in coastal and shallow environments of the tropical sea. The upper sequence (K-1) is represented by the calcareous, clayey, and calcareous-clayey sandstones formed in shallow marine conditions. Maturity degree of the clastic material, which makes up sandstones of the three sequences, decreases from almost monomictic quartz arenites and sublitharenites of the lower sequence to subarkoses of the middle sequence and subarkoses, arkoses, litharenites, and wackes of the upper sequence. All sediments were accumulated in interacratonic sedimentary basins developed successively at passive margins of the Mendeleev microcontinent along with supercontinents Laurussia and Laurasia.