Palaeoecological features of Lower Asselian (Lower Permian) carbonate skeletal mounds in the Pisanyi Kamen’ section (Un’ya River, Northern Urals)

Abstract

Abstract Among the many Upper Carboniferous and Lower Permian reef structures that are known worldwide, a Lower Permian 360 m long succession of reefal rocks in the Urals, interpreted as representing skeletal mounds, stands out for its complexity. The abundance of lime mud material, both in the skeletal mounds and in the adjacent sediments, indicates that they grew below fair‐weather wave base. An important feature of these Lower Permian organic buildups in the Urals is the widespread development of synsedimentary biologically induced cements, which often prevail in the rock volume. One of the most representative (and unique) skeletal mounds sequences in the Northern Urals is the Pisanyi Kamen’ section located on the Un'ya River. This paper aims to identify changes in the character of the palaeocommunity in the Pisanyi Kamen’ section. In the skeletal mounds development in the Lower Asselian interval of the Pisanyi Kamen’ section, seven events are distinguished. These are: (a) stabilisation of a soft sea floor by bryozoans and heterotrophic microbes; (b) colonisation of a hard sea floor by bryozoans and the appearance of abundant bioinduced cements; (c) displacement of bryozoans by a phylloid algae community; (d) appearance of a higher diversity community; (e) the mound top reaching the fair‐weather wave base; (f) collapse of the ecosystem; and (g) recurrent colonisation of a hard sea floor by phylloid algae. This work summarises the current state of knowledge regarding the Lower Permian skeletal mounds structure of the Northern Urals. The description of the ecological succession offers a new tool for the analysis of similar structures.

Keywords

• Asselian
• ecological succession
• Northern Urals
• skeletal mounds