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Über dieses Buch

This book contains the most complete description of the geologic and geophysical data of the structure of Arctic Basin including structures of the earth’s crust, crustal and acoustic basement, and sedimentary cover. The book includes information about extracted and studied cores and samples; observed, processed and interpreted data on geophysical anomalies and different conceptions, and a hypotheses of the origin of the modern Arctic Basin structures. Progress in solving the problems of the Arctic Basin geology is presented in the chapters and include contributions from leading field experts.

Inhaltsverzeichnis

Frontmatter

Chapter 1. The Current State of the Arctic Basin Study

Abstract
The chronology of investigations and geomorphological analysis of the underwater terrain in the abyssal parts of the Arctic Ocean is presented. History of airborne and ship-borne gravity and magnetic surveys is accompanied by the detail technical, quantitative and qualitative analysis of existing datasets and regional potential fields anomalies maps.
The up-to date location maps show the MCS seismic coverage grid inside the Arctic Basin. The important geological structures are highlighted by detail fragments of both TWT and depth converted interpreted seismic sections. The composite velocity models calculated from DSS data along regional geotraverses are also present.
The progress of the seismological observations over several decades presents a telling picture of distribution of hypocenters and focal mechanisms of the modern seismicity related to the mid-ocean spreading zone and its continuation onto the Laptev Sea shelf.
The results of the Arctic Basin deep water seafloor sampling and drilling provide additional input to our knowledge base.
Georgy P. Avetisov, Victor V. Butsenko, Andrey A. Chernykh, Yury G. Firsov, Vladimir Yu. Glebovsky, Evgeny A. Gusev, Artem A. Kireev, Alexey A. Krylov, Anna G. Zinchenko

Chapter 2. Seismic Stratigraphy of Sedimentary Cover

Abstract
Three major unconformities (Regional pre-Miocene, Early Eocene, post-Campanian) are regionally traced in the depressions of the Eurasian Basin. They are dated either by well data (ACEX IODP 302 on the Lomonosov Ridge), or by correlation of their onlaps on acoustic basement with the nearest identifiable linear magnetic anomaly.
The interpretation of pre-Cenozoic stratigraphy in the Central Arctic Uplifts Complex (CAUC) was based on tracing several regional seismic reflectors from seismic lines tied to wells drilled onshore and offshore Alaska into the North Chukchi Trough, with identification of Brookian, Lower Cretaceous and Upper Jurassic unconformities in the latter. This procedure was facilitated by previously established continuity of these unconformities from North Chukchi Trough into Vilkitsky Trough and Podvodnikov Basin. The established reflectors through the system of the Russian MCS profiles were further traced onto the entire Central Arctic Uplifts Complex.
Victor A. Poselov, Victor V. Butsenko, Artem A. Kireev, Oleg E. Smirnov, Sergey M. Zholondz

Chapter 3. Eurasian Basin

Abstract
The Eurasian Basin, ~2000 km long and ~900 km wide, consists of abyssal plains of Nansen and Amundsen Basins separated by mid-oceanic Gakkel Ridge. The magnetic field of the Eurasian Basin consists mostly of linear magnetic anomalies (LMA). According to classic hypothesis, anomalies of Cenozoic sequence, from LMA 24 (chron 24, ~53 Ma) to present, were identified and dated. Steady decline of spreading velocity from 22–27 mm/yr. to 5–9 mm/yr. was established for 53–20 Ma interval; later it grew slightly to 7–12 mm/yr.
At the same time pronounced asymmetry of geological, morphological and bathymetry features of the abyssal depressions, as well as demonstrated by seismic data asymmetry of distribution and thickness variations of sedimentary formations inside them, lead us to conclusion that the considerable part of the Eurasian Basin was probably formed in pre-Cenozoic time.
Vasily A. Savin, Georgy P. Avetisov, Daria E. Artem’eva, Dmitry V. Bezumov, Andrey A. Chernykh, Vladimir Yu. Glebovsky, Gennady S. Kazanin, Alexey L. Piskarev

Chapter 4. Lomonosov Ridge

Abstract
The Lomonosov Ridge is situated between oceanic abyssal regions of the Eurasian Basin, on the one side, and the region of the Central Arctic Uplifts including the abyssal Makarov Basin – on the other. As its morphology and internal structure indicate, it consists of three distinct segments. The shallowest (≤ 400 m) Canada-Greenland segment is composed mostly by felsic and metamorphic rocks (basic igneous – at the part facing Alpha-Ridge). In the Near–Polar segment the ridge has double-crested top with the basin in-between. The structural trend here is at acute angle to the ridge axis and upper crust consists of basic crystalline rocks. The 12 km-thick upper crust of the 150 km-wide Siberian segment of the Lomonosov Ridge consists mainly of felsic and metamorphic rocks.
The ridge’s continental crystalline crust is 20–22 km thick, with upper and lower crusts thickness of about half of the above. Neogene-Pleistocene hemipelagic, Paleogene bathyal and possible Cretaceous deposits comprise the sedimentary cover.
Alexey L. Piskarev, Victor V. Butsenko, Andrey A. Chernykh, Mikhail V. Ivanov, Valery D. Kaminsky, Victor A. Poselov, Vasily A. Savin

Chapter 5. Podvodnikov Basin

Abstract
The vast bathymetric depression of the Podvodnikov Basin lies between the Lomonosov Ridge and Mendeleev - Alpha Ridges, bounded by the East-Siberian Sea shelf from the south and by the Makarov Basin - from the north. Sea depth in the Podvodnikov Basin varies from 800 m to 2700 m in the same direction. The Podvodnikov Basin has a benched structure and is considered to be a part of the terraced continental slope.
The seismic data divide the southern terrace of the Podvodnikov Basin into western and eastern parts, separated by the prominent Geofizikov Spur and its southern continuation as a deeper structure of the acoustic basement. Total thickness of the sedimentary cover here reaches 8 km.
The sedimentary cover of the Podvodnikov Basin is subdivided into six seismic-stratigraphic complexes, dated from late Permian to Holocene by correlation with ACEX well on the Lomonosov Ridge and exploration wells on the Alaska shelf. Integrated geophysical data interpretation and modeling classify the Basin’s crust as stretched continental, with thickness of the crystalline crust from 10 to 23 km.
Oleg E. Smirnov, Victor V. Butsenko, Yury G. Firsov, Vladimir Yu. Glebovsky, Evgeny A. Gusev, Valery D. Kaminsky, Gennady S. Kazanin, Alexey L. Piskarev, Victor A. Poselov

Chapter 6. Makarov Basin

Abstract
Makarov Basin - abyssal plain, 3800 m bsl on average (occasionally–over 4000 m, very close to the depth of the Nansen and Canada Basins), is mostly flat, disturbed only by 800 m-high linear ridge – abyssal continuation of the Marvin Spur. The potential fields anomalies illustrate the variety of structural plans of the Makarov Basin and surrounding regions. Gravity anomalies inside the Makarov Basin display symmetrical pattern relative to the linear positive anomaly parallel to 120°E, flanked by gravity lows on both side.
The total thickness of the sedimentary cover varies from 2 to 4 km. The regional pre-Miocene unconformity RU at the base of the hemipelagic Miocene deposits is traceable through the whole Makarov Basin. The reduced Paleogene complex between the RU and post-Campanian unconformity pCU overlays the Upper Cretaceous and, possibly, older formations. Upper and lower crusts are estimated to be 3–6 km and 3–4 km, accordingly. Total crust thickness is 10–12 km.
Alexey L. Piskarev, Yury G. Firsov, Victor A. Poselov, Oleg E. Smirnov

Chapter 7. Mendeleev and Alpha Ridges

Abstract
The Mendeleev Ridge was formed on the continental crust with total thickness 27–32 km of which the upper crust takes 4–7 km. Continuous chain of progressively seaward deepening bathymetric terraces demonstrate the morphological connection of the Mendeleev Ridge with shallow water regions of the Siberian-Chukchi continental margin. Seismic data reveal that the structure and stratigraphy of the Mendeleev Ridge are affected by intensive normal faulting of acoustic basement creating complex system of grabens and half-grabens. It depicts the Mendeleev Ridge as an extensional structure of Cretaceous age illustrating tectonic evolution of the Central Arctic region. The Miocene-Pleistocene complex, with continuous undisturbed layers of hemipelagic sediments and regional erosional unconformity at its base, drapes the entire Mendeleev Ridge and marks the completion of contemporary morphological modern system of the Mendeleev-Alpha Ridge System.
Victor V. Butsenko, Yury G. Firsov, Evgeny A. Gusev, Valery D. Kaminsky, Sergey P. Kashubin, Alexey L. Piskarev, Victor A. Poselov

Chapter 8. Chukchi Plateau and Chukchi Basin

Abstract
The Chukchi Plateau can be described as a fragment of the continental margin jutted into the abyssal part of the Arctic Ocean. The Chukchi Plateau has the most direct connection with the adjacent shelf of the East Siberian - Chukchi continental margin. The principal structural complexes of the consolidated continental crust continue uninterrupted between the Mendeleev Ridge and Chukchi Plateau with total thickness of 26–29 km and approximately equal thickness of the upper and lower crusts under the Chukchi Plateau.
In the Chukchi Basin the Earth’s crust is 20 km thick with upper crust – 3 km. The Chukchi Basin, with its undisturbed sedimentary complexes, also includes 1200 m of pre- Upper Jurassic (Upper Ellesmerian) formations. Almost complete absence of folding and faults in the Chukchi Basin may point to active sedimentation, not the attenuation of the crust, as a principle cause of its subsidence.
Miocene-Pleistocene complex above the pre-Miocene unconformity continues from the Chukchi Basin to the Chukchi Plateau and marks the end of formation of these present-day morphological structures.
Victor V. Butsenko, Yury G. Firsov, Sergey P. Kashubin, Alexey L. Piskarev, Sergey M. Zholondz

Chapter 9. Extensional Structures of the Central Arctic Uplifts Complex

Abstract
The whole volume of the contemporary information describes the Central Arctic Uplifts Complex as a composite block of continental crust. Rift-related stretching and attenuation of the continental crust is the principal factor dictating the tectonic evolution of this block and its two-phased HALIP magmatism. The most evident signs of the rift-induced strain, − systems of grabens and half-grabens, high-altitude and gently dipping normal faults – are present in the Lomonosov Ridge, Mendeleev Ridge, Chukchi Plateau and on the slopes of the uplifts into the western parts of the Podvodnikov and Chukchi basins. Depocenters of the Vilkitsky Trough (deep-water prolongation of the offshore North Chukchi Trough) and Chukchi Basin are filled with substantially thick Jurassic (or pre- Upper Jurassic) sequence, traceable from the North Chukchi Trough. Jurassic (or pre- Upper Jurassic) deposits are interpreted as relicts of the pre-oceanic Ellesmerian structural stage preserved in near-shelf tectonic depressions. They are strongly affected by rifting only at the elevated parts of the Central Arctic Uplifts Complex, and much less – in the depocenters of the sedimentary depressions.
Victor A. Poselov, Victor V. Butsenko

Chapter 10. Canada Basin

Abstract
Perennial sea-ice cover over much of Canada Basin of the Arctic Ocean has hampered geoscientific studies, but concerted efforts over the past decade– particularly with the use of two ice-breakers working collaboratively – has led to new seismic and sample acquisitions. These studies have revealed extensive non-oceanic basement beneath Canada Basin that coincides with proof of a central spreading axis and limited oceanic crust. Additionally, seismic reflection studies have shown its sedimentologic history and stratigraphic development. High resolution subbottom and multibeam detail have revealed its more recent geologic past, including the extent of ice margins during the Pleistocene and the role of submarine landslides and ocean currents within the basin. Despite this new information, there are still significant challenges in understanding the basin. These challenges result from the fact that the basin did not form by a simple rift/extension scenario, but rather more likely through a complexity of events that included variably oriented extension, trans-tension and transform tectonics. Additionally, emplacement of the high arctic magnetic domain (Alpha Ridge and Mendeleev Rise) masks underlying tectonic structures, and lack of age control inhibits correlation with global events.
David C. Mosher, Deborah R. Hutchinson

Chapter 11. Pliocene-Pleistocene Sedimentation

Abstract
Paleomagnetic data, including the recent high-quality measurements, estimate the average mean sedimentation rate in the Mendeleev Ridge for the last 4 Ma as 1–1.5 mm/kyr, rising slightly towards the shelf seas of northeast Russia. The rates also increase towards the Lomonosov Ridge: in its near-Greenland sector, the Brunhes/Matuyama transition was identified in the sediment core at 330 cmbsf, giving rates of 4.4 mm/kyr for the Brunhes chron.
Recently established presence of volcanic material in bottom sediments indicates active, at times even catastrophic, the Pleistocene volcanic activity in the Arctic Basin. It could be safe to state that the Eurasian Basin in the Arctic Ocean was a scene for at least one such a powerful volcanic eruption with huge volumes of ejected material at ~1.1 Ma.
The study of hydrocarbon molecular markers and the Late Cenozoic sedimentation in the Amerasian continental margin allowed to examine the importance of different processes (terrigeneous denudation, glacial transport, turbidites, oceanic slope contouring currents, submarine erosion, and bedrock material re-deposition) in accumulation of the sedimentary cover.
Daria V. Elkina, Vera I. Petrova, Alexey L. Piskarev, Irina A. Andreeva

Chapter 12. General Features of the Crust and the Sedimentary Cover

Abstract
The wide spectrum of the geophysical information was used for compilation of the “Sediment Thickness Map of the Arctic Ocean”. The sedimentary cover includes all un-deformed Meso-Cenozoic (abyssal Arctic Ocean) or Paleo-Cenozoic (shelves) coilogenic stratified sedimentary complexes from the seafloor to the top of the acoustic basement (TAB) was presented at this Map. The belt of deep depressions located either inside shelves or in continental margin-shelf transition zones ringing the abyssal part of the Arctic Ocean, is clearly visible on the Map.
The demonstrated contemporary crustal thickness map of the Arctic Ocean was compiled using not only existing seismic information and bathymetry but also regional digital gravity dataset. The map vividly illustrates the radical difference in crustal thickness between clearly oceanic regions of the Arctic Ocean (Eurasian and Canada Basins) and remaining parts with continental or transitional types of crust.
Sergey M. Zholondz, Andrey A. Chernykh, Vladimir Yu. Glebovsky, Natalia E. Leonova, Anatoly D Pavlenkin, Victor A. Poselov, Lidia G. Poselova

Chapter 13. Conclusions

Without Abstract
Valery D. Kaminsky, Alexey L. Piskarev, Victor A. Poselov, David C. Mosher
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