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

Motor development related to duration of exclusive breastfeeding, B vitamin status and B12 supplementation in infants with a birth weight between 2000-3000 g, results from a randomized intervention trial

Background: Exclusive breastfeeding for 6 months is assumed to ensure adequate micronutrients for term infants. Our objective was to investigate the effects of prolonged breastfeeding on B vitamin status and neurodevelopment in 80 infants with subnormal birth weights (2000-3000 g) and examine if cobalamin supplementation may benefit motor function in infants who developed biochemical signs of impaired cobalamin function (total homocysteine (tHcy) > 6.5 μmol/L) at 6 months. Methods: Levels of cobalamin, folate, riboflavin and pyridoxal 5´-phosphate, and the metabolic markers tHcy and methylmalonic acid (MMA), were determined at 6 weeks, 4 and 6 months (n = 80/68/66). Neurodevelopment was assessed with the Alberta Infants Motor Scale (AIMS) and the parental questionnaire Ages and Stages (ASQ) at 6 months. At 6 months, 32 of 36 infants with tHcy > 6.5 μmol/L were enrolled in a double blind randomized controlled trial to receive 400 μg hydroxycobalamin intramuscularly (n = 16) or sham injection (n = 16). Biochemical status and neurodevelopment were evaluated after one month. Results: Except for folate, infants who were exclusively breastfed for >1 month had lower B vitamin levels at all assessments and higher tHcy and MMA levels at 4 and 6 months. At 6 months, these infants had lower AIMS scores (p = 0.03) and ASQ gross motor scores (p = 0.01). Compared to the placebo group, cobalamin treatment resulted in a decrease in plasma tHcy (p < 0.001) and MMA (p = 0.001) levels and a larger increase in AIMS (p = 0.02) and ASQ gross motor scores (p = 0.03). Conclusions: The findings suggest that prolonged exclusive breastfeeding may not provide sufficient B vitamins for small infants, and that this may have a negative effect on early gross motor development. In infants with mild cobalamin deficiency at 6 months, cobalamin treatment significantly improvement cobalamin status and motor function, suggesting that the observed impairment in motor function associated with long-term exclusive breastfeeding, may be due to cobalamin deficiency.publishedVersio

Episodic zircon age distributions mimic fluctuations in subduction

Decades of geochronological work have shown the temporal distribution of zircon ages to be episodic on billion-year timescales and seemingly coincident with the lifecycle of supercontinents, but the physical processes behind this episodicity remain contentious. The dominant, end-member models of fluctuating magmatic productivity versus selective preservation of zircon during times of continental assembly have important and very different implications for long-term, global-scale phenomena, including the history of crustal growth, the initiation and evolution of plate tectonics, and the tempo of mantle outgassing over billions of years. Consideration of this episodicity has largely focused on the Precambrian, but here we analyze a large collection of Phanerozoic zircon ages in the context of global, full-plate tectonic models that extend back to the mid-Paleozoic. We scrutinize two long-lived and relatively simple active margins, and show that along both, a relationship between the regional subduction flux and zircon age distribution is evident. In both cases, zircon age peaks correspond to intervals of high subduction flux with a ~10-30 Ma time lag (zircons trailing subduction), illuminating a possibly intrinsic delay in the subduction-related magmatic system. We also show that subduction fluxes provide a stronger correlation to zircon age distributions than subduction lengths do, implying that convergence rates play a significant role in regulating the volume of melting in subduction-related magmatic systems, and thus crustal growth

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

International audienceNo abstrac

Orogenic architecture of the Mediterranean region and kinematic reconstruction of its tectonic evolution since the Triassic

The basins and orogens of the Mediterranean region ultimately result from the opening of oceans during the early break-up of Pangea since the Triassic, and their subsequent destruction by subduction accommodating convergence between the African and Eurasian Plates since the Jurassic. The region has been the cradle for the development of geodynamic concepts that link crustal evolution to continental break-up, oceanic and continental subduction, and mantle dynamics in general. The development of such concepts requires a first-order understanding of the kinematic evolution of the region for which a multitude of reconstructions have previously been proposed. In this paper, we use advances made in kinematic restoration software in the last decade with a systematic reconstruction protocol for developing a more quantitative restoration of the Mediterranean region for the last 240 million years. This restoration is constructed for the first time with the GPlates plate reconstruction software and uses a systematic reconstruction protocol that limits input data to marine magnetic anomaly reconstructions of ocean basins, structural geological constraints quantifying timing, direction, and magnitude of tectonic motion, and tests and iterations against paleomagnetic data. This approach leads to a reconstruction that is reproducible, and updatable with future constraints. We first review constraints on the opening history of the Atlantic (and Red Sea) oceans and the Bay of Biscay. We then provide a comprehensive overview of the architecture of the Mediterranean orogens, from the Pyrenees and Betic-Rif orogen in the west to the Caucasus in the east and identify structural geological constraints on tectonic motions. We subsequently analyze a newly constructed database of some 2300 published paleomagnetic sites from the Mediterranean region and test the reconstruction against these constraints. We provide the reconstruction in the form of 12 maps being snapshots from 240 to 0 Ma, outline the main features in each time-slice, and identify differences from previous reconstructions, which are discussed in the final section

Quantification and restoration of the pre‐drift extension across the NE Atlantic conjugate margins during the mid‐Permian‐early Cenozoic multi‐rifting phases

publishedVersio

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