Association Round Table 2471 volcanics and volcanic derived rocks that closely re­ BONDARlV, V. I., B. S. RO.VIANOVICH, and S. V. semble the strata of the Phelan Creek formation. These CHERKi:SOVA, Research Inst. Geol. of , modern volcanic are mostly inactive and have Leningrad, and V. S. ENOKYAN, Varkuta Complex subsided. Thick limestone-black shale caps are now be­ of Geol. Prospecting Expedition, USSR ing formed on top of the subsiding volcanic plat­ GEOLOGIC S:KUCIUR[ ANB HISTORY OF POTAR URALS, forms. The resulting stratigraphic succession is nearly PAY-KHOY, , AND NORTHERN PE­ identical with the stratigraphic sequence that character­ CHORA DrpRESSiON izes upper deposits throughout the eastern Alaska Range. 1. The late Paleozoic-early Mesozoic fold system of the Urals-Novaya Zemlya and the Paleozoic-Ceno- zoic strata of the Pechora depression formed on a folded basement. 2. Structures within the fold system may be divided BONDAREV, V. I., A. Z. BURSKIY, E. M. KRASI- into (a) the Polar Urals and Pay-Khoy anticlinoria KOV, and L. V. NEKHOROSHEVA, Research Inst. and (b) the structures of Novaya Zemlya. In the main­ Geol. of Arctic, Leningrad, and M. M. ORADOV- land part of the Urals system, a set of foredeep basins SKAYA, Northeastern Regional Geol. Dept., Maga­ is recognized at the junction of the fold system and the dan, USSR depression on the western sides. ORDOVICIAN OF SOVIET ARCTIC 3. The Urals-Novaya Zemlya fold system includes a Ordovician deposits are widely represented within complex of Precambrian, Paleozoic, and early Meso­ the Soviet Arctic. They are known in Novaya Zemlya, zoic (within a foredeep) sedimentary and volcanic Vaygach , Pay-Khoy, , north­ rocks. The Precambrian thickness exceeds 3,000 m, ern Siberian platform. , and and that of ihe Paleozoic, 10,000 m. northeastern USSR. In the western Arctic (Polar Ur- The Paleozoic (Ordovician and younger strata) als-Novaya Zemlya) Ordovician deposits formed the transgressively and unconformably overlies the older base of the Caledonian-Hercynian cycle, and consist of formations. Important hiatuses in the Paleozoic are es­ a very thick variable complex of clastic and carbonate tablished in pre-Late Devonian (Novaya Zemlya), and rocks. in the Late Carboniferous (Pay-Khoy, Novaya Zemlya). In the central Soviet Arctic, the Ordovician is at 4. Volcanic strata of predominantly basic composi­ the base of the stratigraphic column in Severnaya tion occupy much of the Precambrian (Polar Urals, Zemlya, whereas on Taimyr Peninsula and the Siberian Novaya Zemlya, Pay-Khoy) and Late Devonian sec­ platform, it comprises a single depositional cycle with tions. Volcanic rocks of late Paleozoic and early Meso­ the Cambrian. The Ordovician in the region is repre­ zoic ages are found in northeastern Pay-Khoy. sented by predominantly carbonate rocks reaching a An ancient pre-Ordovician and partly pre- thickness of 2,000 m in depressions; in the northern ultrabasic to acid intrusive complex (Polar Urals, Pay- part of the Taimyr Peninsula it consists of graptoUte- Khoy, Novaya Zemlya), a Caledonian (Silurian-Devo­ bearing clastic and carbonate rocks up to 1,000 m nian) complex of ultrabasic, basic, and acid intrusions thick. The Ordovician of Severnaya Zemlya is repre­ (Polar Urals and Novaya Zemlya), and Hercynian sented by variegated elastic and carbonate rocks about basic and acid intrusions (Novaya Zemlya, Polar Ur­ 2,000 m thick. als) are present in this area. Within the eastern Arctic, Ordovician deposits are a 5. Within the fold system the following structural part of the fold fringe of the Kolyma massif and of elements are clearly distinguished: (a) the Polar Urals the Mesozoides of northeastern Chukotsk Peninsula. with an adjacent foredeep of the Urals type; and the Ordovician strata in the northeastern USSR consist of Pay-Khoy anticlinorium, an early Mesozoic structure, carbonate, clastic and carbonate, and wholly terrige­ the strike of which is the same as that of the Baikal- nous clastic sequences. The relations with underlying ides and Novaya Zemlya. The Pay-Khoy and Novaya rocks are uncertain there. Ordovician rock thicknesses Zemlya areas thus have characteristics of both the Ural differ markedly from place to place and reach 5,500 m geosyncline proper and of the Scotland-Scandinavia in some places. Grampian geosyncline joining the Novaya Zemlya Ordovician deposits have been studied in more detail trough on the west. in southern Novaya Zemlya, , northern Pay-Khoy, central Taimyr, in the Norilsk district, and BOSTRoM, KURT, Rosenstiel School of Marine and within the limits of the folded margin of the Kolyma massif. The Ordovician of northern Novaya Zemlya, Atmospheric Sci., Univ. Miami, Miami, Fla. Severnaya Zemlya, and the New Siberian Islands is less ORIGIN OF MANGANESE-RICH LAYERS IN ARCTIC SEDI­ well known. MENTS However, even where Ordovician sections have been A sediment core from the Wrangel abyssal plain (T3 investigated comprehensively and are richly fossilifer- 69-12, lat. 80021.9'N, long. 173°33'W, water depth: ous, the Lower-Middle Ordovician and Ordovician-Si- 2,867 m; core length: 374 cm) was analyzed for CaCoj, lurian boundaries are uncertain because of geologic pe- Mn, PjOj, Al, Fe, and trace elements; in total, 15 cularities of the region. There is no definite solution to samples from the interval 0-350 cm were used for the Cambrian-Ordovician boundary problem. Variable these analyses. Three carbonate layers were found sedimentary facies and diverse zoogeographic provinces (5-16% CaCOj), interspaced by carbonate free strata make regional and interregional correlations drflBcult. (0-2% CaCOa), resembling lithologic variations des­ Nevertheless, recognition of transitional sequences in cribed by Herman in other Arctic cores. fold areas of the Soviet Arctic and the wide interre­ The carbonate-free fractions of the carbonate layers gional distribution of some faunal elements during cli­ show higher contents of Mn (0.4-0.9%) and P3O5 maxes of marine transgression (late Tremadocian and (0.215-0.237%) than the carbonate-poor layers in middle Caradocian) permit rather definite correlations which the corresponding values range between 0.15- for the solution of practical biostratigraphic problems 0.25% and 0.183-0.211%. The Al and Fe values show and correlation with standard sequences elsewhere. no major variations, ranging between 7.5-9.9 and 4.3-