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Explanatory notes for the Tectonic Map of the Kara and Laptev Seas and Northern Siberia (Scale: 1:2 500 000) // M.: Institute of Lithosphere of Marginal Seas RAS, 1998. – 116 p.
Abstract
Тектоническая карта морей Карского и Лаптевых и севера Сибири масштаба 1:2 500 ООО охватывает акватории шельфовых морей и южное окончание Евразийского бассейна Северного Ледовитого океана, а также многочисленные острова и прилегающую часть суши. В пределах карты выделяются следующие основные структурные элементы. В центре расположен Сибирский кратон с фундаментом протерозойского возраста. Наиболее древние породы фундамента в пределах карты обнажаются в Анабарском щите и в Оленекском поднятии. Породы основания перекрыты осадочным и вулканогенным чехлом, среди которого особое место занимает трапповая формация и одновозрастные с ней щелочноультраосновные интрузии, а также кимберлиты. В пределах
кратона установлены импактные структуры. К западу от Сибирского кратона располагается ЗападноСибирский бассейн, структура которого осложнена триасовыми рифтами. Дно Карского моря
в восточной части слагает гренвильская Карская плита, структуры которой поднимаются над уровнем
моря в пределах многочисленных островов, в том числе, архипелагов Северной Земли и Нордшельда.
На юге Карская плита граничит по Центрально-Таймырскому аккреционному поясу с Сибирским
кратоном, а на востоке - с Южно-Карской субокеанической впадиной и гренвильской Свальдбарской
плитой. К востоку от Карской плиты в пределах моря Лаптевых расположена северо-восточная окраина Сибирского кратона, подтвергшаяся сложным деформациям в мезо-кайнозойское
время. От структур Евразийской впадины и хребта Гаккеля шельф кратона отделен трансформным
разломом Чарли. Анализируется нефтегазоносность региона.
Объяснительная записка объемом 127 стр., 36 илл., библ. 281 назв. Карта и разрезы к ней на 2 листах.
Supplementary resource (1)
... The eastern boundary with the Anabar-Lena CTSE (Khudoley et al. 2021) is traced along a zone of abrupt thinning of Mesozoic sediments. The Siberian Craton, as a part of Rodinia, had a developed Mesoproterozoic-early Neoproterozoic passive continental margin (Vernikovsky 1996;Bogdanov et al. 1998;Pisarevsky and Natapov 2003;Vernikovsky et al. 2004). Mesoproterozoic strata of the CTSE, using analogies with coeval formations of the Siberian Craton, could consist of carbonate and siliciclastic sediments (Fig. 3). ...
... Pogrebitsky (1971) connected the cause this change to the Taimyr Orogeny, which culminated in the early Permian. Modern structural, petrological, geochronological and palaeomagnetic data prove conclusively that this change in sedimentation was related to the collision of the Siberian Craton with the Kara microcontinent (Vernikovsky 1992(Vernikovsky , 1996Vernikovsky et al. 1995;Bogdanov et al. 1998;Metelkin et al. 2000Metelkin et al. , 2005Metelkin et al. , 2015Khain 2001). Strike-slip zones with large displacements, along which the Kara microcontinent was 'sliding' during the entire early Paleozoic, finally led to the collision of the Kara and Siberian plates, and to the subsequent formation of the imbricated Taimyr-Severnaya Zemlya FTB and growth of the related orogen (Metelkin 2012). ...
... A possible cause of the Late Jurassic-Early Cretaceous inversion of the CTSE could be related to the late Mesozoic collision of the Kolyma-Omolon Superterrane with the eastern margin of the Siberian Craton and formation of the Verkhoyansk FTB east of the CTSE. This compressional deformation from the SE affected the Yenisei-Khatanga CTSE, especially its eastern part, where it caused the formation of a system of elongated swells (Bogdanov et al. 1998). It is also possible that the counter-clockwise rotation of the Siberian Craton was another cause of the inversion and transpressive deformation of the Mesozoic infill of the Yenisei-Khatanga CTSE at the Jurassic-Cretaceous boundary (Timofeev et al. 2011). ...
The Yenisei-Khatanga Composite Tectono-Sedimentary Element (YKh CTSE) is located between the Siberian Craton and the Taimyr-Severnaya Zemlya fold-and-thrust belt. The total thickness of the Mesoproterozoic-Cenozoic sediments of YKh CTSE reaches 20 to 25 km. They are divided into four tectono-sedimentary elements (TSE): (i) Mesoproterozoic-early Carboniferous Siberian Craton continental margin, (ii) middle Carboniferous-Middle Triassic syn-orogenic Taimyr foreland basin, (iii) late Permian-Early Triassic syn-rift, and (iv) Triassic-Early Paleocene post-rift. The last one is the most important in terms of its petroleum potential and is the most drilled part of the CTSE. Its thickness accounts for half of the total thickness of YKh CTSE. The margins of the post-rift TSE and the inner system of inversion swells and adjacent troughs and depressions were shaped by three tectonic events: (i) middle Carboniferous-Middle Triassic Taimyr orogeny, (ii) Late Jurassic-Early Cretaceous Verkhoyansk orogeny, (iii) Late Cenozoic uplift. These processes led to more intense migration of hydrocarbons, the trap formation and their infill with hydrocarbons. Triassic, Jurassic, and Lower Cretaceous source rocks are mostly gas-prone, and among 20 discovered fields in Jurassic and Cretaceous plays, 17 are gas or mixed-type fields.
... The structures of the north-western margin of the Siberian craton have attracted the attention of geologists for over a hundred years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and many others. The earliest and most essential questions on the study area are: (a) How did the Taimyr-Severnaya Zemlya folded area form-a key structure of the Artic, and is it a part of the Siberian craton; (b) what are the sequence and stages of its formation, how is the formation of this folded area related to the formation of the Yenisei-Khatanga basin; (c) what serves as the basement for the latter. ...
... Tectonic map of the north-western part of the Siberian craton, the Taimyr folded area and the Yenisei-Khatanga basin. Composed using References [5,6] with additions by the authors. 1-boundary of the Yenisei-Khatanga basin along outcrops of Early Jurassic and younger rocks; 2-Kara microcontinent (a) including metamorphosed and deformed flyschoid passive margin sediments (NP-Є) of the North Taimyr Zone (b); 3-7-the Central Taimyr accretionary belt: 3-gneiss complexes of cratonic terranes with 940-850 Ma granitoids; 4-terranes of carbonate shelves (MP(?)-NP); 5-island arc terranes, ophiolites and plagiogranites (750-630 Ma), and accretionary wedge complexes; 6-molasses (NP), carbonate, black shales, shelf and hemipelagic sediments (NP 3 -C); 7-offshore part of the belt; 8-syncollisional (306-300 Ma) and postcollisional (264-258 Ma) granites; 9-depths of the Siberian craton crystalline basement and of the deformed, mostly Paleozoic rocks within the Yenisei-Khatanga basin and the West Siberian basin; 10-isohypses (depth in km) of the seismic basement roof: (a)-established, (b)-inferred; 11-13-Siberian traps (P 2 -T 1 ): 11-dolerites and their differentiates; 12-alkaline ultramafic rocks and carbonatites; 13-flood basalts and associating volcanogenic-sedimentary deposits; 14-zones of continental rifting and range formation: I-Tanama-Malokhet, II-Rassokhin and III-Balakhnin from [17] 2-sandy-argillaceous sediments; 3-mudstones, and shales; 4-limestones; 5-dolomites; 6-basalts, tuffs, terrigenous rocks (P 2 -T 1 ); 7-folded structure of the crystalline basement Kara microcontinent (shown figuratively); 8-gneiss-granite and granulite-mafic complexes of the crystalline basement; 9-faults; 10-roof of the seismic basement: (a) Established, (b) inferred from indirect data and single observations. ...
... According to results of deep seismic sounding, the Moho boundary depth under the Yenisei-Khatanga basin varies from 27-33 km in the central part to 36-38 km under the North-Siberian monocline and to 40-43 km under Taimyr [6,23,24]. The crystalline basement is supposedly composed of metamorphic rocks of Archean-Paleoproterozoic age. ...
The geodynamic development of the northwestern (Arctic) margin of the Siberian craton is comprehensively analyzed for the first time based on our database as well as on the analysis of published material, from Precambrian-Paleozoic and Mesozoic folded structures to the formation of the Mesozoic-Cenozoic Yenisei-Khatanga sedimentary basin. We identify the main stages of the region's tectonic evolution related to collision and accretion processes, mainly subduction and rifting. It is demonstrated that the prototype of the Yenisei-Khatanga basin was a wide late Paleozoic foreland basin that extended from Southern Taimyr to the Tunguska syneclise and deepened towards Taimyr. The formation of the Yenisei-Khatanga basin, as well as of the West-Siberian basin, was due to continental rifting in the Permian-Triassic. The study describes the main oil and gas generating deposits of the basin, which are mainly Jurassic and Lower Cretaceous mudstones. It is shown that the Lower Cretaceous deposits contain 90% of known hydrocarbon reserves. These are mostly stacked reservoirs with gas, gas condensate and condensate with rims. The study also presents data on oil and gas reservoirs, plays and seals in the Triassic, Jurassic and Cretaceous complexes.
... He also identified the Anabar-Khatanga Saddle (AKhS) as a separate structural domain located between the Khatanga and Anabar rivers, later often referred to as the Khatanga Saddle. However, on more recent tectonic maps, the AKhS has been included in the Anabar-Lena Basin and not shown as a separate structure (Parfenov 1990;Bogdanov et al. 1998). Nowadays, both structures are usually separated from each other, and the area between the Anabar and Lena rivers is usually called the Anabar-Lena (or, sometimes, Lena-Anabar) Basin or Province, whereas the AKhS occupies the area between the Khatanga and Anabar rivers (e.g. ...
Anabar-Lena Composite Tectono-Sedimentary Element (AL CTSE) is located in the northern East Siberia extending for c. 700 km along the Laptev Sea coast between the Khatanga Bay and Lena River delta. AL CTSE consists of rocks from Mesoproterozoic to Late Cretaceous in age with total thickness reaching 14 km. It evolved through the following tectonic settings: (1) Meso-Early Neoproterozoic intracratonic basin, (2) Ediacaran - Early Devonian passive margin, (3) Middle Devonian - Early Carboniferous rift, (4) late Early Carboniferous - latest Jurassic passive margin, (5) Permian foreland basin, (6) Triassic to Jurassic continental platform basin and (7) latest Jurassic - earliest Late Cretaceous foreland basin. Proterozoic and lower-middle Paleozoic successions are composed mainly by carbonate rocks while siliciclastic rocks dominate upper Paleozoic and Mesozoic sections. Several petroleum systems are assumed in the AL CTSE. Permian source rocks and Triassic sandstone reservoirs are the most important play elements. Presence of several mature source rock units and abundant oil- and gas-shows (both in wells and in outcrops), including a giant Olenek Bitumen Field, suggest that further exploration in this area may result in economic discoveries.
... The Severnaya Zemlya Archipelago is located on the edge of the Kara Shelf, between the Kara and Laptev seas, and north of Taimyr; it includes four large islands (October Revolution, Bol'shevik, Komsomolets and Pioneer) and a small group of islands in the southwest, the Sedov Archipelago. Together with the northern part of the Taimyr Peninsula, Severnaya Zemlya represents the exposed part of the North Kara Plate (Bogdanov et al., 1998). Reconstruction of the Early Palaeozoic history of this region is controversial; some authors (e.g. ...
The Furongian (Late Cambrian) Kurchavinskaya Formation of October Revolution Island, Severnaya Zemlya Archipelago, Arctic Russia, contains two distinctive morphotypes of the trace fossil Cruziana, both of which we assign to Cruziana semiplicata. A wider form shows characteristics typical of this ichnospecies with inner and outer lobes and marginal ledges. A narrow form has only an inner lobe with siculate, often interfering scratch-marks, and rare, narrow marginal ridges. This narrow form, which shows characters in common with Cruziana tortworthi, probably represents burrowing in a strongly head-down orientation. The record from October Revolution Island provides additional evidence that the palaeogeographical distribution of Cruziana semiplicata is not restricted to Gondwana, but also extend to parts of Baltica and North Kara. Cruziana semiplicata is known from the Furongian and Tremadocian of Gondwana, whereas on Baltica it is known only from the Furongian
... Within the Turukhansk area (often referred to as the Turukhansk Uplift), up to 4.5 km of Mesoproterozoic (?)-Neoproterozoic strata occur in three north-trending, faultbounded and east-transported blocks where the formations either dip gently westwards or occur in asymmetrical synclines with a gentle eastern limb and subvertical, partly truncated, western limbs (Petrov & Semikhatov 2001). These sandstones, shales, calcareous mudstones, dolostones, and limestones, including reef-bearing carbonate units were deposited on a passive continental margin (Petrov & Veis 1995;Petrov & Semikhatov 1997Sergeev et al. 1997;Bogdanov et al. 1998;Pisarevsky & Natapov 2003). The Turukhansk sediments include Neoproterozoic silicified microfossils and stromatolite assemblages (Petrov & Veis 1995;Sergeev et al. 1997;Knoll & Semikhatov 1998). ...
The Siberian Craton is bounded by fold-and-thrust belts involving Neoproterozoic (locally Mesoproterozoic) complexes on the southern (Baikal-Vitim), western (Yenisey Ridge and Turukhansk-Igarka), northern (Taimyr), and eastern (Verkhoyansk) sides. This paper focuses on the geological structure and evolution of these formations. Previous and new geochronological data show that passive continental margins existed around most of the Siberian Craton during the early Neoproterozoic and possibly the late Mesoproterozoic. Between about 850-760 Ma, the southern, western and northern passive margins of the Siberian Craton were transformed into active margins. Middle-late Neoproterozoic island arcs and ophiolites were formed between c. 750-650 Ma along these margins; they are inferred to have been obducted onto the Siberian continental margin at c. 600 Ma, prior to late Vendian deposition. New ion microprobe U-Pb ages of ophiolitic rocks from Taimyr's Central domain are presented. The Neoproterozoic record in the Cretaceous Verkhoyansk fold-and-thrust belt indicates that the eastern part of the Siberian Craton remained a passive continental margin during the Neoproterozoic and Palaeozoic. Baltica-Siberia relationships are also discussed.
The Northern West Siberian-South Kara Composite Tectono-Sedimentary Element (NWSSK CTSE) occupies over 1 mln. km ² of the northern West Siberian Basin and the South Kara Basin. It formed as a result of the latest Permian - earliest Triassic crustal extension following thermal subsidence. The Early Triassic palaeorifts are buried under 10-12 km-thick post-rift Middle Triassic - Quaternary siliciclastic sediments. In the Tithonian - Early Berriasian period, a deep-water anoxic depression formed in the West Siberian Basin and accumulated organic-rich carbonate-siliceous Bazhenov shales, that are the main source of hydrocarbons.
The West Siberian Basin, including the NWSSK CTSE, is one of the major petroleum provinces worldwide. Oil and gas deposits have been identified in Paleozoic carbonate basement rocks, Triassic, Jurassic, and Cretaceous reservoirs. The main gas reserves are concentrated in the Lower Aptian-Cenomanian play. Significant gas and oil reserves are located in the Berriasian - lowest Aptian and Jurassic plays.
The CTSE comprises 18-20% of the world known gas reserves and provides approximately 90% of the total Russian natural gas, which is 22% of the world gas extraction. In this chapter we provide a summary of the CTSE geology and petroleum geology based on bulk results mainly published in the Russian literature.
Emplacement of large volumes of (sub)volcanic rocks during the main pulse of the Siberian Traps occurred within <1 m.y., coinciding with the end-Permian mass extinction. Volcanics from outside the main Siberian Traps, e.g. Taimyr and West Siberia, have since long been correlated, but existing geochronological data cannot resolve at a precision better than ~5 m.y. whether (sub)volcanic activity in these areas actually occurred during the main pulse or later. We report the first high precision U-Pb zircon geochronology from two alkaline ultramafic-felsic layered intrusive complexes from Taimyr, showing synchronicity between these and the main Siberian Traps (sub)volcanic pulse, and the presence of a second Dinerian-Smithian pulse. This is the first documentation of felsic intrusive magmatism occurring during the main pulse, testifying to the Siberian Trap’s compositional diversity. Furthermore, the intrusions cut basal basalts of the Taimyr lava stratigraphy hence providing a minimum age of these basalts of 251.64 ± 0.11 Ma. Synchronicity of (sub)volcanic activity between Taimyr and the Siberian Traps imply that the total area of the Siberian Traps main pulse should include a ~300 000 km2 area north of Norilsk. The vast aerial extent of the (sub)volcanic activity during the Siberian Traps main pulse may explain the severe environmental consequences.
The dramatic rise in the world oil and gas demand has led to concerns about the energy future for mankind. In the twenty-first century the sedimentary basins of the Arctic Ocean will play a leading role as petroleum provinces, including its Russian shelf areas. This article deals with the characteristics and assessment of resources in the Russian sector of the Arctic Ocean offshore areas. One can predict with 0.90 probability that the Arctic Ocean initial in-place hydrocarbon resources exceed 90 billion tons oil equivalent (toe). The assessments lead to the conclusion that during these years a petroleum production industry will develop on the Arctic Ocean Shelf.
Sixty-three maps illustrate geodynamic evolution and development of palaeoenvironments and palaeolithofacies of the Circum-Arctic region during Phanerozoic times. After the break-up of Rodinia and Pannotia in the Early Palaeozoic, the major Arctic plates Baltica, Siberia and Laurentia drifted from their original position around the South Pole towards the Supercontinent Pangea, which existed in the equatorial position during Late Palaeozoic and Early Mesozoic times. During the Mesozoic and Cenozoic plates gathered around newly formed Arctic Ocean. Large continental masses were assembled from major plates and numerous small plates and terranes on the northern hemisphere and around the North Pole. All the continents were by now connected. Carbonates were abundant in Siberia and Laurentia during Palaeozoic times. Clastic sedimentation prevailed during Mesozoic and Cenozoic times. The distribution of lithofacies shows climatic change associated with continental assembly and disassembly as well as with the steady northward drift of the continents.
The Laptev Sea is a part of the Eurasia Arctic margin between the Taimyr Peninsula and the Novosibirsk Islands. It is the southern termination of the Nansen-Gakkel spreading ridge and thus the location of structural features resulting from a continental margin/spreading ridge intersection. It is a natural laboratory for addressing the processes of an initial breaking-up of the continents.
In this paper we will demonstrate what is now well-established concerning the Laptev Sea Shelf geology and what remains to be solved. We are utilizing the data collected by the authors during several onshore and offshore expeditions to the Laptev Sea from 1985 to 1991. The available data of the MAGE's 1986-1987 seismic surveys were used also for preparation of the structural maps.
The 3500-m-thick sequence of volcanic rocks at Noril'sk, formed during a brief interval (∼1 m.y.) at the Permian/Triassic time boundary (∼251 Ma), represents the earliest part of the ∼6500-m-thick sequence presently ascribed to the Siberian flood-basalt province. It is composed of picritic and basaltic lavas of both low-Ti and high-Ti parentage. Extensive geological, geochemical, and isotopic study of the lava sequence and related intrusions allows detailed reconstruction of its petrogenesis. Various crustal-related processes - fractionation, crustal contamination, sulfide separation, and magma mixing - participated in the formation of the lavas. The geochemical and isotopic characteristics indicative of these processes, as well as mantle-related signatures of lava compositions, are discussed. Based on these characteristics, detailed interpretations of lava genesis and evolution throughout the Noril'sk sequence are presented. Eight varieties of lavas are recognized to be primitive, similar in composition to primary mantle melts; they varied from low-Mg basalts to olivine tholeiites or picrites, with normal tholeiites predominating. The primitive lavas are subdivided into four groups (magma types) on the basis of trace-element ratios (principally. Gd/Yb, Th/U, La/Yb, Ta/La, Ti/Sc, and V/Yb) and isotopic data. Three of the groups include both basaltic and picritic primitive lavas (with low-Mg basalts present in one of them), whereas the fourth group is represented exclusively by tholeiites. Distinctions among the groups cannot be related to degree of melting, and isotopic data indicate that none of the magma types could have formed by mixing or contamination of other types. Apparently, only differences in source composition and/or depth of melting can explain the magmatic diversity. This multitude of primitive magma types may be explained by melting in different layers of the upper mantle, which is complexly layered beneath Siberia to depths of 270 km. Moreover, no clear boundary between lithosphere and asthenosphere is evident in the deep seismic profile. A large-scale event is necessary to account for melting in different parts of the upper mantle and formation of the great volume of the Siberian flood basalts in ∼1 m.y. Extension, caused by ascent of a mantle plume, would provide a reasonable explanation, but no plume-related uplift is documented in north-central Siberia prior to, or during, eruption of the volcanic sequence.
Based on interpretation of marine geologic and geophysical data, there is a widespread, systematic development of rift-and-graben systems in the structure of the Eurasian Arctic continental margin. The characteristics of the largest structures are presented, including the Varanger, Bear-Olga, Estern Barents, Kara-West Sibera, Laptev-Kolyma and Chukchi-Bering Sea.
The lower continental crust (10–40 km deep), modeled from geophysical data and kimberlite xenoliths studies, is assumed to be composed of mafic granulites with seismic velocities as high as Pv=6.35–7.05 km/s, densities of 2.85–3.08 g/cm3 (Meissner, 1986) and radioactive heat productions of A=0.48–0.53 µW/m3 (Rudnick, 1992, Kremenetsky et al., 1986). In contrast the upper crust is enriched with highly radioactive granite batholiths and granite-migmatite domes (Taylor and McLennan, 1985) and shows Pv=6.06 km/s, an average density of 2.75 g/cm3 and A=1.33–1.75 µW/m3. The lower crust, brought to the surface by upthrusting along decollements, appears to be composed of thinly banded isoclinally folded granulites with intermediate to mafic and ultramafic compositions (Percival et al., 1992, Rutter and Brodie, 1992 and Zingg et al., 1990). Dates from the lower crustal rocks are “very poorly constrained” (Downes, 1993). This paper discusses the isotopically dated two-stages of lower crust formation and the absence of the upper crust in the Anabar shield.
The Siberian craton extends from Lake Baikal on the south for over 2500 km to the Arctic Ocean on the north, and from the Yenisey River on the west to the Sea of Okhotsk on the east The borders of the craton are major Phanerozoic suture zones that formed during the aggregation of Pangea in the late Paleozoic and early Mesozoic. The oldest suture is between the southwestern margin of the Siberian craton and the Central Asia Paleozoic orogenic belt. This orogenic belt was formed by accretion of Late Proterozoic and early Paleozoic arc systems to the southwestern margin of the Siberian craton beginning in the Late Riphean and continuing into the mid-Paleozoic. During this collision in the Devonian, the Barguzin terrane composed of Paleozoic and Late Proterozoic rocks was thrust onto the southern margin of the Siberian craton. During the mid to late Mesozoic, terranes collided with Siberia along the southeastern and eastern borders (directions based on present position) forming the Mongolia-Okhotsk and Verkhoyansk orogenic belts. Although the western border of the Siberian craton is covered with Mesozoic cratonic sediments, geophysical data suggest the presence of a tectonic boundary in the subsurface west of Noril'sk.
Within the Caledonian complexes of northwestern Spitsbergen, high PT formations provide UPb zircon ages of 965±1 Ma of a metagranite and 955±1 Ma of a corona gabbro, indicating the influence of Grenvillian activity in the area. Various isotopic systems suggest that these rocks were partially derived by reworking of ancient crust (as old as Archaean). Eclogites and felsic agmatite indicate latest Proterozoic magmatic or metamorphic events (625−5+2 and 661±2 Ma, respectively) by UPb zircon dating. The eclogitic metamorphism age is not fully constrained and ranges between 540 and 620 Ma; this occurred prior to the superimposed Caledonian metamorphism, indicated by a part of the KAr and RbSr mineral cooling ages. The new data and other evidence of Precambrian tectonothermal activity on Svalbard suggest that the Early Palaeozoic and Late Proterozoic successions exposed elsewhere on Svalbard may also be underlain by Grenvillian or older basement rocks. Relationships to other Grenvillian and older terrains in the Arctic are reviewed.
Exposures of Proterozoic crust in Alaska are rare; howeover, isotopic data from younger rocks derived from unexposed basement suggest that Proterozoic (or older) crust may underlie large areas of northern Alaska. Late Proterozoic orthogneisses, Late Proterozoic to Cambrian metasedimentary rocks, and Devonian granitic orthogneisses in the western Brooks Range have Nd- and Sr-isotope compositions consistent with derivation, at least in part, from Middle to Early Proterozoic crust. The range of observed isotopic compositions may be explained by mixing mantle-derived magmas, or melts of juvenile crust, with melts of Proterozoic crust in varying proportions. Nd isotope systematics of the Late Proterozoic metasedimentary rocks are identical to reported values from Early Proterozoic metaplutonic rocks in the Idono Complex and Kilbuck terrane in SW Alaska, and to clastic sedimentary rocks from the Belt Supergroup in Montana. -from Authors