The Connecticut Valley-Gaspé (CVG) trough represents a major, orogen-scale Silurian-Devonian basin of the Northern Appalachians. From Gaspé Peninsula to southern New England, the CVG trough has experienced a contrasting metamorphic and structural evolution during the Acadian orogeny. Along its strike, the CVG trough is characterized by increasing strain and polyphase structures, and by variations in the intensity of regional metamorphism and contrasting abundance of ~ 390 to 370 Ma granitic intrusions. In southern Quebec and northern Vermont, a series of NW-SE transects across the CVG trough have been studied in order to better understand these along-strike variations. Detailed structural analyses, combined with phase equilibria modeling, Raman spectrometry and muscovite 40 Ar/ 39 Ar dating highlight a progressive and incremental deformation involving south-north variation in the timing of metamorphism. Deformation evolves from a D 1 crustal thickening event which originates in Vermont and progresses to southern Québec where it peaked at 0.6 GPa/380°C at c. 375 Ma. This was followed by a D 2 event associated with continuous burial in Vermont from 378 Ma to 355 Ma, which produced peak metamorphic conditions of 0.85 GPa/630 o C and exhumation in Quebec from 368 to 360 Ma. The D 3 compressional exhumation event also evolved from south to north from 345 to 335 Ma. D 1 to D 3 deformation events form part of a continuum with an along-strike propagation rate of  50 km/m.y. During D 1 , the burial depth varied by more than 15 km between southern Quebec and Vermont, and this can be attributed to the occurrence of a major crustal indenter, the Bronson Hill Arc massif, in the New England segment of the Acadian collision zone.

No abstract

We present here a study based on the Anisotropy of Magnetic Susceptibility (AMS) and magnetic mineralogy carried out on the composite core MD17&18taken from the eastern levee of the active channel of the middle Bengal Fan in the Indian Ocean. Based on C-14 dating, the sedimentary sequence covers 9.8 ka in 39 m of sediment. It therefore records at very high resolution the variations in continental material exported to the ocean by the Ganges-Brahmaputra river system during the Holocene.This sequence was divided into two units according to turbidite activity: Unit 1 from 9.8 to 9.2 ka cal. BP representing 39 m of coarse-grained turbidite sequences (coarse silts to fine sands) and extremely high sedimentation rates. Unit 2 of 9.2 ka cal. BP to the present characterized by a sharp decrease in the sedimentation rate, the presence of fine-grained turbidites characterized by strong decrease in the ln(Ti/Ca) ratio.Our AMS results indicate that the magnetic fabric is highly sensitive to the mode of deposition. The turbidite sequences are clearly characterized by very high F and Pj values, not only of the coarse-grained turbidite levels in unit 1, but also of the fine turbidites in unit 2. We suggest that this strong degree of anisotropy is the result of the strong and rapid deposition during the turbidite sequences which induces an additional compaction effect.Furthermore, low temperature SIRM measurements revealed that the magnetic minerals representative of the Ganges and Brahmaputra drainage area are magnetite, hematite and goethite. A higher supply in fine-grained magnetite was observed during the turbidite sequences in phase with an increase in sediment grain size.

<p>The Sperchios - North Evia Gulf rift system is WNW-ESE directed and participates to the widespread crustal extension induced by the respectively southward and south-westward Nubian and Ionian slabs retreat, and by the extrusion of the Anatolia-Aegean microplate. This crustal stretching, active at least since the early Pliocene, is partly coeval with the North Anatolian Fault (NAF) propagation through the Marmara Sea and the North Aegean domain. At the western termination of the NAF, in the studied area, the domain is widely heterogeneous as it has been previously deformed by successive tectonic events during Hellenic orogeny, from Middle Jurassic to Paleogene times. The low elevation of the Internal Zones in respect to the External Zones of Hellenides suggest that the Frontal Thrust of the Internal Zones, that crosscut the Sperchios Rift, plays a major role in the distribution of rift systems within that area. The Sperchios-North Evia Gulf rift developed over the internal Zones and was driven by at least two major extensional episodes. The first one is characterised by a NNE-SSW extensional direction while the second, still active, is NNW-SSE to N-S. This change in direction can be associated to a modification of the tectonic setting within the Aegean Plate or can be a consequence of clockwise rotation of the whole western Aegean domain.</p><p>The WATER survey (Western Aegean Tectonic Evolution and Reactivations), conducted in July-August 2017 onboard the R/V “Téthys II”, allowed to acquire more than 1300 km of very high resolution seismic reflection profiles (Sparker 50-300 Joules) around North Evia Island (North Evia Gulf, Oreoi Channel and Skopelos Basin). The new dataset issued from this survey illustrates structural patterns that can be correlated with onland fault systems.</p><p>The interpretation of this new seismic data allowed us to precise the main trends of the North Evia Gulf rift deformation. For example, the rift bordering faults show rapid longitudinal changes in terms of offsets and of their main tilting polarity. Our structural analysis results, together with the kinematic analysis of onshore fault zones, give detailed constraints on the rift structural organisation as well as on the relative chronology of tectonic episodes.</p><p>Furthermore, these results provide important data in order to discuss the relations of some major rift structures with other crustal structures inherited from earlier deformation in the Hellenides, and also to consider the deformation patterns in the south-western prolongation of the North Anatolian Fault system during Pliocene to Quaternary times. We discuss the relations between various generations of crustal-scale structures and propose that the variations in the rift asymmetry were triggered, during its initial development, by the presence of older crustal heterogeneities.</p>