Abstract The Kozhim carbonate bank, a 380-m-thick Upper Carboniferous-Lower Permian carbonate buildup exposed in the northeastern Komi Republic, Russia, grew on a topographic high near the margin of the Ural Trough. The carbonate bank is composed of intermixed radiaxial cement-rich biohermal facies and associated skeletal wackestones-packstones-grainstones. Traditionally the carbonate buildup has been referred to as a reef, but percentages of biohermal facies are uncertain and organic boundstones are not present, and in this study it is referred to as a carbonate bank. Bank growth was initiated in the Late Kasimovian-Early Gzhelian in response to subsidence of the Ural Trough. In the Gzhelian-Asselian lower part of the bank section, biohermal facies are composed of fenestrate bryozoan- Tubiphytes -radiaxial calcite cementstones. Within the bioherms and associated bioclastic facies, bryozoans, Tubiphytes, echinoderm ossicles, and brachiopods are common to abundant; and ammonoids, gastropods, and smaller foraminifera are sparse. Fusulinids, calcareous algae, and calcisponges occur locally at some horizons but are lacking through most of the section. These periodic occurrences of warmer-water biota probably indicate relative sealevel changes, but no evidence of subaerial exposure was found, and bank deposition appears to have been continuous. In the Late Asselian-Sakmarian upper part of the bank, the fenestrate bryozoan- Tubiphytes -radiaxial cementstones grade into and intermix with Palaeoaplysina bafflestones- cementstones. Palaeoaplysina -phylloid algal bafflestones-cementstones are the dominant facies near the top of the buildup. The Gzhelian-Asselian fenestrate bryozoan -Tubiphytes cementstone bioherms grew in a relatively cool-water deep-ramp to slope setting. The gradual transition in the upper bank from cooler-water facies to a warmer-water Palaeoaplysina -phylloid algal biohermal community suggests upward bank growth into shallower and warmer water. The upper Palaeoaplysina-rich part of the Kozhim bank is commonly cited as an outcrop analog for Upper Carboniferous-Lower Permian hydrocarbon reservoirs in the adjacent Timan-Pechora Basin that contain similar Palaeoaplysina bioherm facies. However, those reservoir facies are generally associated with shallow-water grainstone shoal deposits that often display evidence of repeated periods of subaerial exposure, and they did not undergo pervasive early diagenetic cementation. Palaeoaplysina bioherm complexes and associated flanking grainstone deposits exposed on Spitsbergen and Bjornoya in the Norwegian Barents Sea are probably better outcrop analogs for the Timan- Pechora reservoir sections.

Abstract The development of the Frasnian (Upper Devonian) reef complexes of the southern Timan and Pechora region of northern European Russia is described. Barrier reef complexes progressively prograded eastwards during the Frasnian but the carbonate complexes were interrupted many times by regressive events. Using new conodont and ammonoid bio-stratigraphical dating, the timing of reef building episodes has been established which enables international correlation with other similar Devonian areas. Basinal anoxic and hypoxic deposits associated with the reef complexes of the Domanik facies provide the major hydrocarbon source rocks of the region and the palaeoenvironmental interpretation of these is discussed. Initial transgressions appear to have been associated with the global Taghanic Onlap of the late Givetian. The new level for the base of the Frasnian and Upper Devonian lies in the Timan Formation, after the deposition of which marine conditions mostly prevailed in the area examined until the late Frasnian when a sharp regression occurred with no evidence of the typical Kellwasser facies of Western Europe and other areas. Transgressive pulses initiated ammonoid biofacies in the Regional Sargaev Stage and the widespread Timan Event was marked by the spread of Timanites faunas. A significant deepening event which initiated the Domanik facies correlates approximately with the Middlesex black shale of New York and the main development of the Domanik facies with the Rhinestreet black shale of New York. There are faunal and floral peculiarities of the area, shown by endemic genera and rather different ranges of cosmopolitan species than elsewhere, which complicates precise international correlation. Nevertheless, several of the main sea-level deepening pulses of the Frasnian, documented in North America, Western Europe, North Africa and Australia, are recognizable and these are thought to represent eustatic events.

Abstract The Lower Palaeozoic sequences, unconformably overlying the Timanides of Timan, Pechora, Pai-Khoi, Vaigach, Novaya Zemlya and the Polar, Northern, Middle and Southern Urals are described and interpreted with regard to their stratigraphy, sedimentation, structure and biogeography. These mainly shallow marine sedimentary successions, with associated igneous rocks (largely alkaline), are Ordovician in age, reaching back into the Late Cambrian in some areas, particularly in the east, along the front of the Urals. They were deposited during rifting of Baltica's northeastern margin and subsequent development of a passive continental margin. The underlying, mainly Neoproterozoic basement of turbidites in the west and calc-alkaline volcanites and ophiolites further east are briefly referred to, with particular emphasis on the age of the youngest rocks. Based on these data, a Timanian orogenic belt can be traced along the northeastern and eastern margin of the East European Craton. The timing of orogeny can be constrained to the Vendian, perhaps extending into the Early Cambrian.

Abstract As important components of extinct as well as modern reefs, the measurement of changes in the composition of reef biota is crucial in order to evaluate the influence of extrinsic factors on the marine communities. The dramatic abiotic changes in the eastern and northern Pangea was mirrored by a gradual transition from a photozoan to a heterozoan association and the appearance of cool- (temperate-) water carbonates both in reef and carbonate ramp environments. Analyses of large skeletal and microbiotic components as well as microfacies succession were used for detailed explanation of reef structure, especially for lesser-known heterozoan skeletal mounds. The youngest skeletal mounds are recognized in the Roadian. The stable isotope data demonstrated a negative oxygen shift between latest Sakmarian and late early Artinskian coinciding with the end of P2 glaciation. The multiplicative nature of the event included the series of successive changes of extrinsic factors such as ice melting in interglacial episodes, eustatic ocean level rise, change of oceanic circulation and decrease of water temperature. The late Artinskian and subsequent Kungurian climatic impacts in the Northern Hemisphere were irreversible for the photozoan biota and prevented its further development. Roadian (Guadalupian) bryonoderm extended skeletal mounds developed in rather warm-water environments.

Abstract Pennsylvanian and Lower Permian organic carbonate buildups mostly lack large massive reef-building organisms, but rather were constructed by relatively small organisms, such as calcareous algae, calcisponges, and bryozoans, Microbial encrustation and submarine cementation often played significant roles in the construction of the buildups. These buildups consist of a spectrum of mound and reef types whose organic and inorganic compositions are controlled mainly by seawater temperature and light availability, which in turn are related directly to paleolatitude and/or water depth, and growth position. Lower Upper Carboniferous (Bashkirian-lower Moscovian, Morrowan-lower Desmoinesian), shallow shelf to shelf-margin, organic carbonate buildups are mostiy broad low banks and mounds constructed by calcareous algae (e.g., Dvinella/Donezella, Komia, Cuneiphycus , phylloid algae), Chaeleles sponges, and microbialites, In Japanese seamount reefs, which were located in high-energy open sea settings, rugose corals, tabulate corals, and chaetetids were the important constructors. Steep platform slopes during this time were apparently supported mainly by microbialite and synsedimentary cementation. Upper Upper Carboniferous (Desmoinesian-Virgilian/“Bursumian”, Moscovian-Gzhelian/Orenburgian) tropical shallow-water shelf and shelf-margin carbonate buildups are predominantly bafflestones composed mostly of erect udoteacean phylloid algae. In contemporaneous, slightly deeper-water, mound-flank to intermound areas, communities of calcareous sponges, laminar encrusting red algae, and bryozoans built smaller boundstone reefs. In Lower Permian (Wolfcampian, Asselian-Sakmarian) tropical paleolatitudes, those two buildup communities merged and constructed bafflestone-boundstono reefs in shelf-margin settings that were composed of a framework (baffler guild) of erect phylloid algae, calcareous sponges, and fenestellid and ramose bryozoans, which were encrusted by (binder guild) laminar red algae ( Archaeolithophyllum), Archaeolithoporella, Tuibiphytes , and fistuliporid bryozoans (Chiorosponge association). Many tropical shelf-margin buildups are rich in originally aragonitic botryoidal radial fibrous cements, and in some, heliosponges and specialized Permian reef brachiopods are locally abundant. Such Lower Permian aigal-calcisponge-cement reefs are known throughout the Permian circum-equatorial belt, from present-day southwestern and midcontinent North America, to the circum-Mediterranean region, to southeast and East Asia. That integrated reef-building community radiated and persisted through the rest of Permian time, reaching its acme of development in Middle and Upper Permian tropical reefs, such as the Capitan Reef of the Permian Basin. At more subtropical to warm temperate paleolatitudes, upper Upper Carboniferous to Lower Permian shallow-water shelf to shelf-margin buildups were constructed mainly by Palaeoaplysma , with varying proportions of intermixed phylloid algae, and sometimes botryoidal radial fibrous cements (Chloroforam association). Paleoaplysina buildups are known from around the northern margin of the paleocontinent Laurasia, which includes the present-day northwestern United States, Arctic Canada, the Barents Sea region, and the Russian Ural Mountains region. As seen in Arctic Canada and Russia, contemporaneous, somewhat deeper-water, upper slope buildups were constructed by fenestrate bryozoans and Tubiphytes , and those buildups commonly have pervasive originaily calcitic radiaxial cements tones (Brynoderm to Brynoderm-extended association). The Palaeoaplysina -phylldalgal algal and fenestra tebryozoan-Tubiphytes reef communities intermixed in buildups at intermediate water depths, and the latter buildup type sometimes shallowed upward into the former buildup type. In adjacent deeper-water, lower slope to basinal settings, siliceous sponges constructed organic carbonate buildups (Hyalosponge association) that commonly included intermixed bryozoans and brachiopods at intermediate depths. Most shallow-water, tropical and subtropical buildups were composed predominantly of originally aragonitic organic and inorganic elements (e.g., phylloid algae, Palacoaplysina , calcareous sponges, botryoidal radial fibrous cements), whereas buildups in deeper and/or cooler water were dominated by Mg-calcite constituents (e.g., bryozoans, Tubiphytes , radiaxial cements). Many of the cooler- water biotic elements were also contributors to warm-water reefs, but there they were usually greatly diluted by the more prolific tropical biota.