Alexandra Abrajevitch

Alexandra Abrajevitch
Russian Academy of Sciences | RAS

PhD

About

47
Publications
7,047
Reads
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1,240
Citations
Additional affiliations
April 2011 - present
Australian National University
Position
  • ARC Fellow
June 2008 - March 2011
Kochi Univesity, Japan
Position
  • Researcher
January 2005 - May 2008
University of Michigan

Publications

Publications (47)
Article
Full-text available
Hematite carries magnetic signals of interest in tectonic, paleoclimatic, paleomagnetic, and planetary studies. First‐order reversal curve (FORC) diagrams have become an important tool for assessing the domain state of, and magnetostatic interactions among, magnetic particles in such studies. We present here FORC diagrams for diverse hematite sampl...
Article
Full-text available
Abstract Determination of hematite contributions to sedimentary magnetizations is an important but difficult task in quantitative environmental studies. The poorly crystalline and fine-grained nature of hematite nanoparticles makes quantification of their concentrations in natural environments challenging using mineralogical and spectroscopic metho...
Article
Zebra Rock, a decorative stone remarkable for its unusual pattern of regularly spaced reddish bands and rods with white background, is found within the Neoproterozoic succession in East Kimberley, Western Australia. The unusual pigment distribution suggests that precipitation of hematite, or its precursor phase, occurred in a single episode. Magnet...
Conference Paper
Full-text available
The Paleocene-Eocene Thermal Maximum (PETM, ≈55.8±0.2 Ma) is marked by a global change in carbon cycle and rapid warming and is considered as an analogue for anthropogenic climate changes. The cause and timing of the PETM have hitherto remained under debate. Common explanations are the North Atlantic Igneous Province volcanism (NAIP) and/or to the...
Article
Full-text available
The normal evolution of the Earth has been punctuated in the past by sudden, dramatic events. Changes in the Earth's rotational speed, asteroid impacts, violent volcanic eruptions, earthquakes, tsunami, and extreme climatic events have periodically caused changes in the environment, which often harmed dominant life forms, but also triggered rapid b...
Article
Understanding the contribution of biogenic magnetic particles into sedimentary assemblages is a current challenge in palaeomagnetism. It has been demonstrated recently that magnetic particles produced through biologically controlled mineralization processes, such as magnetosomes from magnetotactic bacteria, contribute to the recording of natural re...
Article
The Deccan Volcanic Province (DVP) was built up by three major phases of eruptions; the most voluminous of which, the Deccan Phase 2, encompassed the Cretaceous-Paleogene (KT) boundary. Deccan eruptions have been implicated as a contributor to the end-Cretaceous mass extinction, however, mechanism by which volcanic activity affected biota remains p...
Article
The Deccan Volcanic Province (DVP) was built up by three major phases of eruptions; the most voluminous of which, the Deccan Phase 2, encompassed the Cretaceous–Palaeogene (KT) boundary. Deccan eruptions have been implicated as a contributor to the end-Cretaceousmass extinction, however, mechanism by which volcanic activity affected biota remains p...
Article
Under suitable conditions, magnetofossils (the inorganic remains of magnetotactic bacteria) can contribute to the natural remanent magnetization (NRM) of sediments. In recent years, magnetofossils have been shown to be preserved commonly in marine sediments, which makes it essential to quantify their importance in palaeomagnetic recording. In this...
Article
Full-text available
The end-Triassic mass extinction event is regarded as one of the fi ve largest extinction events of the Phanerozoic. The emerging consensus points to volcanic activity at the Central Atlantic Magmatic Province (CAMP) as the ultimate cause of the extinction, yet the underlying mechanisms and the nature of global environmental changes that accompanie...
Article
It is a common concept that different tectonic units in the western part of the Central Asian Orogenic Belt were united into the landmass of the Kazakhstania continent in the Paleozoic but many important details of its history remain enigmatic and controversial. Recently published paleomagnetic data from this region demonstrate that the ~ 2000 km l...
Article
A significant margin-parallel translation of terranes is postulated by all models for tectonic evolution of the East Asian continental margin, although the timing and magnitude of displacements of individual elements are poorly constrained as yet. The West Sakhalin Basin—a forearc basin associated with the Cretaceous volcanic arcs—is one of the dis...
Article
A rock magnetic study of the upper 40 m of the ODP section 133-820A recovered at the outer edge of the northeastern Australian continental margin shows that downcore variations in magnetic parameters are diagenetically driven and correlate with the changes in global sea-level. We identified intervals enriched in single-domain magnetite in the studi...
Article
To better constrain Baltica's position within Pangea, we conducted a palaeomagnetic study of Permo-Triassic dykes from the Oslo Graben, as a follow-up to an initial, but rather limited, study by Torsvik and colleagues in 1998. The age of these so-called Lunner dykes had previously been determined as ∼240 Ma in that study, but details in their analy...
Article
Full-text available
A rock magnetic study of the upper 40 m of the Ocean Drilling Program Site 133-820A recovered at the outer edge of the northeastern Australian continental margin shows that downcore variations in magnetic parameters are diagenetically driven and correlate with the changes in global sea level. We identified intervals enriched in single-domain (SD) m...
Article
Bedded chert is the only sediment type representative of the Paleozoic to early Mesozoic pelagic marine environment. Because of their association with ophiolites and island arc rocks, presence of datable microfossils and paleohorizontal reference provided by well-developed bedding surfaces, bedded chert sequences are often targeted for paleomagneti...
Article
The end-Triassic mass extinction event is regarded as one of the ``big five'' extinctions of the Phanerozoic, yet the cause for the biotic turnover remains elusive; proposed explanations for the extinction event range from gradualistic to catastrophic mechanisms. In the Inuyama area, Japan, the Tr-Jr boundary interval is found within a continuous c...
Article
Paleomagnetic results obtained from rocks of Ediacaran age in several localities in Laurentia and Baltica persistently display co-existence of two magnetization components, one shallowly and the other steeply inclined. Both components pass criteria for a primary magnetization while geological considerations and radiometric age dating indicate that...
Article
Relative abundances of goethite and hematite in marine sediments have been increasingly used in reflectance spectrometry studies to infer the precipitation regime at the source area of detrital sediments. This interpretation is contingent on the assumption that the ratio of these minerals is not modified by diagenetic processes. Our rock-magnetic s...
Article
Studies of modern tropical soils have demonstrated that the relative abundance of pedogenic goethite and hematite is controlled by moisture availability. To evaluate the utility of a G/H ratio as a paleo-precipitation proxy, we conducted a rock-magnetic study of paleosol samples from a known paleo-environmental context. Goethite and hematite conten...
Article
An apparently complete carbonate-rich Cretaceous–Tertiary boundary interval in ODP section 119-738C-20R-5 from the southern Kerguelen Plateau provides a unique insight into processes of magnetization acquisition in marine carbonates. The boundary interval is characterized by a 1-m-thick clay-rich zone. Distinct depositional lamina are preserved wit...
Article
Subduction-related volcanics of Devonian age form an inverted U-shaped belt in Kazakhstan and yielded paleomagnetic inclinations indicating coherent northern hemisphere paleolatitudinal positions between 15 and 40 degrees North during the Mid-Late Devonian. The directions, on the other hand, show a large but systematic variation, in which declinati...
Conference Paper
Baltica, the stable part of the European continent, was located in a paleolatitude range of 9-45 degrees N during the Permo-Triassic. When compared with paleolatitudes inferred for Gondwana's northern margin (up to 20 degrees N), the classical Pangea-A configuration (Bullard et al., 1965) is not possible, because Gondwana and Laurussia would overla...
Article
Full-text available
The tectonic and paleogeographic evolution of the Ural-Mongol belt between the cratons of Baltica, Siberia, and Tarim is key to the formation of the Eurasian composite continent during Paleozoic time, but the views on this complicated process remain disparate and sometimes controversial. A study of three volcanic formations of mid-Silurian, Lower t...
Article
An apparently complete carbonate-rich Cretaceous-Tertiary boundary interval in ODP section 119-738C- 20R-5 from the southern Kerguelen Plateau provides a unique insight into processes of magnetization acquisition in marine carbonates. The boundary interval is characterized by a 1-m-thick clay-rich zone. The basal 15 cm of this zone is finely lamina...
Article
The Kazakhstan orocline, a horseshoe-shaped belt with volcanic arcs of Devonian (external) and late Paleozoic (internal) age, is thought to have formed as a result of convergence between the cratons of Siberia, Baltica and Tarim leading to the amalgamation of Eurasia. Paleomagnetic and geologic data indicate that in the Middle Devonian the arc, whi...
Article
The Kazakhstan orocline, a pair of concentric horseshoe-shaped volcanic arcs of Devonian (external) and late Paleozoic (internal) age, is thought to have formed during the amalgamation of Eurasia. Paleomagnetic investigations of several volcanic complexes ranging in age from Silurian to Permian are described in Chapters 2, 3 and 4 of this thesis. T...
Article
Various climatic proxies indicate that significant change in the Indian monsoon system occurred at ~ 7-8 Ma. The exact nature of this change is debated and involves either the intensification of the monsoon or increased aridity in the region. We conducted a rock magnetic study of the Bengal Fan sediments to estimate the variation in the monsoon int...
Article
A prominent feature of the central part of the Ural–Mongol orogenic belt is a series of concentric horse-shoe shaped volcanic arcs, with the youngest arc on the inside. This structure was long-suspected to be an orocline, but unequivocal evidence for this was lacking, mainly because paleomagnetic results of suitable age from this area remained spar...
Article
Sediments of the Dunkard Gr. were deposited in the Appalachian foreland basin during the Pennsylvanian and Early Permian, an interval encompassing the long reverse polarity Kiaman chron. Lithofacies in the Dunkard Gr. in eastern Ohio and western West Virginia include lenticular and sheet-form cross-bedded micaceous sandstones, coal, mottled red and...
Article
The Ural-Mongol orogenic belt played an important role in the formation of Eurasia, and is considered to be key to understanding the processes of continental crust formation and super-continental amalgamation. The prominent feature of the central part of the belt is a series of concentric horse- shoe shaped volcanic arcs, with the youngest arc on t...
Article
Since 1999, independently derived geophysical and geological models have been published arguing for an intra-oceanic subduction system along essentially the entire width of the India–Eurasia collision belt. This idea conflicts with earlier proposals, where in the eastern part of the convergence zone Neotethyan mid-ocean ridge-generated lithosphere...
Article
Full-text available
The Bainang terrane, an intra-oceanic island arc subduction complex into which Tethyan oceanic rocks were accreted during the Cretaceous, is preserved within the Yarlung–Tsangpo suture zone of Tibet. The lithostratigraphic succession established from field mapping records a long history of sedimentation in different portions of the central Tethyan...
Article
Full-text available
A palaeomagnetic investigation of lower Eocene (ca. 52 Ma) London Clay Formation cemented mudstones from Sheppey (SE England) has yielded a mean direction of Dec. = 1.1 • , Inc. = 43.2 • , where N = 9, α95 = 6.8 • and K = 58.5. This apparently high-quality direction (Q-factor = 5) has an associated palaeopole of 178.6 • E, 63.7 • N, where A 95 = 6....
Article
Full-text available
Well-preserved, abundant radiolarians provide high-precision biostratigraphic age constraints on the timing of the eruption of ophiolitic basalts exposed along the Yarlung–Tsangpo suture zone in southern Tibet. Dazhuqu terrane ophiolites were generated in an intra-oceanic supra-subduction zone setting within a relatively short (<10 Ma) interval fro...
Chapter
Full-text available
Ophiolitic rocks distributed along the Yarlung Tsangpo suture zone in southern Tibet are the few remaining fragmentary remnants of many thousands of kilometres of the ocean space that formerly existed between India and Eurasia. Portions of mid-Jurassic and mid Cretaceous intra-oceanic island arcs can be recognized amongst those rocks that have been...
Article
Full-text available
A palaeomagnetic investigation of lower Eocene (ca. 52 Ma) London Clay Formation cemented mudstones from Sheppey (SE England) has yielded a mean direction of Dec. = 1.1 • , Inc. = 43.2 • , where N = 9, α95 = 6.8 • and K = 58.5. This apparently high-quality direction (Q-factor = 5) has an associated palaeopole of 178.6 • E, 63.7 • N, where A 95 = 6....
Article
Full-text available
Detailed investigations along the Yarlung Tsangpo suture zone, Tibet result in the following conclusions. (1) Arc, forearc, and subduction complex elements of at least one intra-oceanic island arc which once lay within Tethys and accreted to India prior to its collision with Asia are preserved within the suture. (2) Collision-related tectonic mélan...
Article
Full-text available
Detailed investigations along the Yarlung Tsangpo suture zone, Tibet result in the following conclusions. (1) Arc, forearc, and subduction complex elements of at least one intra-oceanic island arc which once lay within Tethys and accreted to India prior to its collision with Asia are preserved within the suture. (2) Collision-related tectonic mélan...
Conference Paper
Full-text available
The Dazhuqu terrane comprises several massifs of mid-Cretaceous ophiolitic rocks with the signature of a supra-subduction zone setting. It is associated with the Zedong (island arc) and Bainang (accretionary wedge) terranes, and with these terranes is interpreted to represent remnants of a Jurassic-Cretaceous south-facing intra-oceanic subduction s...
Article
Thesis (M. Phil.)--University of Hong Kong, 2003. Includes bibliographical references (leaves 81-94).

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