Cretaceous-Tertiary geodynamics: a North Atlantic exercise

New reconstructions are presented for the Cretaceous–Early Tertiary North Atlantic using a combination of palaeomagnetic, hotspot and magnetic anomaly data. We utilize these reconstructions in an analysis of previously described misfits between the North Atlantic Plate elements at successive intervals during this time period. We are able to achieve reasonable overlap between the hotspot and palaeomagnetic reconstructions between 40 and 95 Ma and thus are able to support the idea that the Indo–Atlantic hotspots are relatively stationary. Small, but systematic discrepancies for this time interval can readily be modelled with a long-term, octopole non-dipole field contribution (G3 = g₃⁰/g₁⁰ = 0.08). However, hotspot and palaeomagnetic reconstructions for the Early Cretaceous North Atlantic show substantial differences that cannot be explained by constant, non-dipole fields and we favour an explanation for these discrepancies in terms of true polar wander (TPW) triggered by mantle instabilities between 125 and 95 Ma; this constitutes the only identifiable event of significant TPW since the Early Cretaceous. Taken in the context of available geochronological and geological data and seismic tomography from the region, the 95–40 Ma reconstructions and their time-consequent geological products are interpreted in terms of specific conditions of mantle-crust coupling and global plate motions/tectonic activity. Highlights from these reconstructions show uniform NE movement of the coupled North American, Greenland and Eurasian plates from 95 to 80 Ma; a marked cusp in the paths for all three elements at 80 Ma where the three plates simultaneously change direction and follow a uniform NW-directed motion until c. 20 Ma when Eurasia diverges NE, away from the still-NW-moving Greenland and North American elements. Positioning of the Iceland plume beneath the spreading-ridge at 20 Ma may have increased upwelling below the ridge, increased the ridge-push, and caused a NE shift in the absolute direction of Eurasia

Конкурентоспроможність машинобудівних підприємств на ринку залізничного рухомого складу

Охарактеризовано распределение производственных мощностей и потребителей вагоно-строительной продукции на экономических рынках СНГ. Дана оценка конкурентной среды в подотрасли машиностроения железнодорожного подвижного состава на макро и микроуровне, выявлены факторы риска и обоснованы мероприятия, ориентированные на укрепление конкурентоспособности исследуемых предприятий. Ключевые слова: машиностроительное предприятие, конкурентоспособность, рынок, железнодорожный подвижной состав.Охарактеризовано розподіл виробничих потужностей і споживачів вагонобудівної продукції на економічних ринках СНД. Наведено оцінку конкурентного середовища в підгалузі маши-нобудування залізничного рухомого складу на макро і мікрорівні, виявлено фактори ризику й обґрунтовано заходи, орієнтовані на зміцнення конкурентоспроможності досліджуваних підприємств. Ключові слова: машинобудівне підприємство, конкурентоспроможність, ринок, залізничний рухомий склад.The paper characterizes production capacities and consumers of wagon products on the economic markets of CIS countries. The competition environment in the sector of railway rolling stock building on macro and micro-level was assessed, the factors of risk were identified, and measures oriented to streng-thening the competitiveness of the enterprises under investigation are well-grounded. Keywords: machine-building enterprise, competitiveness, market, railway rolling stock

Global plate motion frames: Toward a unified model

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94772/1/rog1664.pd

Reply to Ali & Aitchison's comment on 'Restoration of Cenozoic deformation in Asia, and the size of Greater India'

International audienceNo abstrac

Support for an “A‐type” Pangea reconstruction from high‐fidelity Late Permian and Early to Middle Triassic paleomagnetic data from Argentina

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/1/jgrb16956-sup-0006-fs04.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/2/jgrb16956-sup-0005-fs03.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/3/jgrb16956.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/4/jgrb16956-sup-0008-fs06.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/5/jgrb16956-sup-0004-fs02.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/6/jgrb16956-sup-0007-fs05.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/94802/7/jgrb16956-sup-0003-fs01.pd

Baltica. A synopsis of vendian-permian palaeomagnetic data and their palaeotectonic implications

In light of recent additions to the Palaeozoic palaeo-magnetic data-base, particularly for the Ordovician era, a revised apparent polar wander (APW) path for Baltica has been constructed following a rigorous synthesis of all Late Precambrian-Permian data. The APW path is characterized by two prominent loops. Firstly, a Late Precambrian-Cambrian loop probably relating to a rifting event and secondly, a younger loop relating to a Mid-Silurian (Scandian) collision event. These features imply major change in plate-tectonic reconfiguration.Baltica probably represented an individual continental unit in Early Palaeozoic times and was positioned in high southerly latitudes in an "inverted" geographic orientation. In such a reconstruction Baltica was separated from the northern margin of Gondwana by the Tornquist Sea and from Laurentia by the Iapetus Ocean. The Tornquist Zone is thus interpreted as a passive or dextral transform margin during the early Palaeozoic.While undergoing counter-clockwise rotations (up to 1.6[deg]/Ma), Baltica drifted northward through most of the Palaeozoic; except for a short period of southerly movement in Late Silurian-Early Devonian times after collision with Laurentia. Rapid movements in latitude (up to 9 cm/yr) are noted in Late Precambrian/early Palaeozoic times and significant decrease in velocities throughout Palaeozoic time probably reflect the progressive amalgamation of a larger continent by Early-Devonian (Euramerica) and Permian (Pangea) times.The Tornquist Sea had a principal component of palaeo-east-west orientation. Hence it is difficult to be precise in the timing of when micro-continents such as Eastern Avalonia and the European Massifs ultimately collided along the southwestern margin of Baltica. These micro-continents are considered to have been peripheral to Gondwana (in high southerly latitudes) during the Early Ordovician. Eastern Avalonia clearly had rifted off Gondwana by Llanvirn-Llandeilo times and may have collided with Baltica during Late Ordovician times, although the present available Silurian palaeomagnetic data from Eastern Avalonia may suggest collision in Late Silurian times.Across the Iapetus facing margin of Baltica, Laurentia was situated in equatorial to southerly latitudes during most of the Lower Palaeozoic. These continents collided in Mid-Silurian times, i.e. a first collision between southwestern Norway and Greenland/Scotland which gave rise to the early Scandian Orogeny (425 Ma) in southwestern Norway possible followed by a later, but less dramatic, Scandian event in northern Norway at around 410 Ma. Since Baltica was geographically inverted in early Palaeozoic times, the collisional margin could not have been a margin that once rifted off Laurentia as assumed in a number of plate-tectonic models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29743/1/0000080.pd

Reconstructions of the continents around the North Atlantic at about the 60th parallel

Abstract Late Carboniferous^Early Tertiary apparent polar wander (APW) paths (300^40 Ma) for North America and Europe have been tested in various reconstructions. These paths demonstrate that the 500 fathom Bullard et al. fit is excellent from Late Carboniferous to Late Triassic times, but the continental configuration in northern Pangea changed systematically between the Late Triassic (ca. 214 Ma) and the Mid-Jurassic (ca. 170 Ma) due to pre-drift extension. Best fit North Atlantic reconstructions minimize differences in the Late Carboniferous^Early Jurassic and Late CretaceousT ertiary segments of the APW paths, but an enigmatic difference exists in the paths for most of the Jurassic, whereas for the Early Cretaceous the data from Europe are nearly non-existent. Greenland's position is problematic in a Bullard et al. fit, because of a Late Triassic^Early Jurassic regime of compression ( s 300 km) that would be inherently required for the Norwegian Shelf and the Barents Sea, but which is geologically not defensible. We suggest a radically new fit for Greenland in between Europe and North America in the Early Mesozoic. This fit keeps Greenland`locked' to Europe for the Late Paleozoic^Early Mesozoic and maintains a reconstruction that better complies with the offshore geological history of the Norwegian Shelf and the Barents Sea. Pre-drift (A24) extension amounted to approximately 450 km on the Mid-Norwegian Shelf but with peak extension in the Late Cretaceous. ß 2001 Published by Elsevier Science B.V

The ∼270 Ma palaeolatitude of Baltica and its significance for Pangea models

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86901/1/j.1365-246X.2011.05061.x.pd

New Late Permian paleomagnetic data from Argentina: Refinement of the apparent polar wander path of Gondwana

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95004/1/ggge1994.pd

Continental crust beneath southeast Iceland

The magmatic activity (0–16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland—and especially the Öræfajökull volcano—is characterized by a unique enriched-mantle component (EM2-like) with elevated 87Sr/86Sr and 207Pb/204Pb. Here, we demonstrate through modeling of Sr–Nd–Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2–6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume