Structure of upper Lochkovian (Lower Devonian) Lop'yu Kyrta organic buildup (Ilych river, Northern Urals)

Studied rocks from Lop'yu Kyrta rock at the Ilych River (Northern Urals) are represented mainly by biohermal limestones, lime sandstones, gravelite-sandstones and breccias. Among Biohermal limestones stromatolitic ones are predominate, coral, Fistulella -microbial, and stromatoporoid-microbial ones are rarer. The comparison and correlation of transect series allow us to establish the landscape-morphological zonation of Lop'yu Kyrta buildup, an outer slope and a reef-flat are distinguished. The reef-flat was differentiated into the reef-crest, gravel-sand shoals, a reef core and a back-reef. In general, the stromatolite structure of framework and the characteristic reef zonation can attribute Lop'yu Kyrta to a specific type of buildups - a stromatolite reef. It was established that the Lop'yu Kyrta stromatolite reef had much in common with the modern microbial Highburne Cay reef at the Great Baham Bank. Stratigraphically and geographically similar Upper Silurian stromatolite reefs from the Northern Urals and Alaska are considerably different by their frameworks architecture from Lop'yu Kyrta buildup.