Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
The Early Palaeozoic Orogen of SE China consists of three litho-tectonic elements, from top to bottom: a sedimentary Upper Unit, a metamorphic Lower Unit and a gneissic basement. The boundaries between these units are flat lying, south directed, ductile decollements. The lower one is coeval with an amphibolite facies metamorphism (M1). The belt is reworked by migmatite-granite domes, high-temperature metamorphism (M2) and granitic plutons related to post-orogenic crustal melting. We date here the syn-M1 ductile shearing at 453 +/- 7 Ma by U-Th/Pb method on monazite. Previous ages and our new
ISSN: 0954-4879

hal-00420901
https://hal.archives-ouvertes.fr/hal-00420901
https://hal.archives-ouvertes.fr/hal-00420901/document
https://hal.archives-ouvertes.fr/hal-00420901/file/Faureetal-TerraNova-2009.pdf
DOI : 10.1111/j.1365-3121.2009.00888.x

Éditeur(s) : HAL CCSD University of Chicago Press
Résumé : International audience
In the North China block, the south Liaodong Peninsula massif is an elliptical metamorphic core complex (MCC) with a long axis trending NE‐SW. In cross‐section view, it is asymmetric, with a steeply dipping northwestern flank and a gently dipping southeastern flank. It consists of three lithotectonic units: a gneissic migmatite unit, a Paleo‐ to Meso‐Proterozoic micaschist‐slate unit, and a Neoproterozoic to Mesozoic sedimentary cover. Three deformation events related to extensional tectonics are distinguished in the study area: D1 is a ductile deformation related to the exhumation of the MCC; the following event, D2, corresponds to the development of recumbent folds formed during the early exhumation of the MCC; and the youngest event, D3, corresponds to brittle normal faulting that controlled the opening of a Cretaceous continental half‐graben basin. A pre‐D1 event characterized as northward verging is interpreted as the result of N‐S shortening that occurred in the Late Triassic during the final stages of the collision between the North and South China blocks. The ductile and brittle structures were developed coevally, with synkinematic plutonism and formation of half‐grabens. New 40Ar/39Ar and U/Pb Cretaceous ages obtained from the mylonitic granodiorite, gneissic migmatite, orthogneiss, and granite indicate that the south Liaodong Peninsula MCC is contemporaneous with other Cretaceous extensional structures, such as numerous syntectonic plutons bounded by ductile normal faults, MCC, and half‐graben basins, described in eastern China. Among the several hypotheses proposed to account for the Mesozoic extension along the eastern margin of Eurasia, lithosphere convective removal appears to be the most likely.
ISSN: 0022-1376

insu-00362879
https://hal-insu.archives-ouvertes.fr/insu-00362879
https://hal-insu.archives-ouvertes.fr/insu-00362879/document
https://hal-insu.archives-ouvertes.fr/insu-00362879/file/WeiLin-TheJournalofGeology-2008.pdf
DOI : 10.1086/527456

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The investigation of deformation rates on a mountain piedmont can provide key information for improving our understanding of the overall dynamics of a mountain range. Here, we estimate the shortening rate absorbed by a Quaternary emergent detachment fold on the southeastern piedmont of the Tianshan (China). Our work is primarily based on new 10Be cosmogenic exposure dating of deformed alluvial surfaces. The method we have developed combines depth profiling with sampling of surface cobbles, thereby allowing exposure time, erosion rate and inheritance to be simultaneously constrained. The exposure ages of the uppermost uplifted alluvial surfaces are around 140±17 ka140±17 ka, 130±9 ka130±9 ka and 47±9 ka47±9 ka, from west to east. A terrace lying below the 140 ka surface is dated at 65±5 ka65±5 ka. The ages of the uplifted and folded alluvial surfaces were then combined with estimates of shortening obtained using two distinct methods: (1) the excess area method, where sedimentation rates, extracted from magnetostratigraphic studies, are used to determine the amount of sedimentation after the abandonment of the river; and (2) a folding model derived from sandbox experiments. The late Pleistocene shortening rates are shown to be between 0.4±0.1 mm/yr0.4±0.1 mm/yr and 0.8±0.5 mm/yr0.8±0.5 mm/yr on the western part of the fold and 2.1±0.4 mm/yr2.1±0.4 mm/yr along its central part. The central part of the frontal Yakeng anticline therefore accommodates up to 25% of the total shortening currently absorbed across the whole Eastern Tianshan range (8 mm/yr). However, this situation seems to have prevailed for only the last 150 ka, as the shortening rate absorbed by this nascent fold was previously ten times slower. While the initiation of folding of the Yakeng anticline can be traced back to 5.5 Ma ago, the basinward migration of the active deformation front onto the Yakeng fold is a relatively recent phenomenon and appears to be diachronous from west to east, probably in relation to the tectonic activity of the folds in the hinterland.
ISSN: 0012-821X

hal-01306997
https://hal.archives-ouvertes.fr/hal-01306997
DOI : 10.1016/j.epsl.2015.11.041

Éditeur(s) : HAL CCSD
Résumé : International audience
The host-parasite genera Proformica-Rossomyrmex present four pairs of species with a very wide range of distribution from China to Southeastern Spain, from huge extended plains to the top of high mountains. Here we review (1) the published data on these pairs in comparison to other slave-makers; (2) the different dispersal ability in hosts and parasites inferred from genetics (chance of migration conditions the evolutionary potential of the species); (3) the evolutionary potential of host and parasite determining the coevolutionary process in each host-parasite system that we treat to define using cuticular chemical data. We find a lower evolutionary potential in parasites than in hosts in fragmented populations, where selective pressures give advantage to a limited female parasite migration due to uncertainty of locating a host nest. A similar evolutionary potential is detected for hosts and parasites when the finding of host nests is likely (i.e., in continuous and extended populations). Moreover, some level of local adaptation at CHC profiles between host and parasite exists independently of the kind of geographic distribution and the ability of dispersal of the different populations. Similarity at CHC profiles appears to be a trait imposed by natural selection for the interaction between hosts and slave-makers.
Psyche

hal-01322574
https://hal.archives-ouvertes.fr/hal-01322574
DOI : 10.1155/2013/541804