Éditeur(s) : Imp. N. Telhomme Imp. N. Telhomme ( Port-au-Prince )
Résumé : (Statement of Responsibility) par Her-ra-ma-el pseud..
Haiti
Haiti

AAN2704
01435575
000116887

Éditeur(s) : Gauthier-Villars
Résumé : Phosphorite genesis correlates in a general way with elevated sea level and warm climate and is therefore influenced by plate tectonics and continental drift. Phosphorite genesis correlates more specifically with transgression -- a result of the interaction of continental hypsometry, tectonic perturbation and eustatic effects -- whereby a small number of shallow slope and shelf sites are available for phosphate fixation. Phosphorite genesis correlates with warm climate. Oceanic anoxic events (OAE's : episodes of world-wide deposition and preservation of organic carbon), which also correlate with particularly high sea level stands, generally do not coincide with major phosphorogenic episodes. In contrast to the assertions above, the permian Phosphoria Fromation was deposited during a marked overall global low-stand of sea level. However, the phosphatic sequences were laid down during brief transgressive episodes.
Oceanologica Acta, Special issue (0399-1784) (Gauthier-Villars), 1981

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00245/35660/34169.pdf
http://archimer.ifremer.fr/doc/00245/35660/

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Temperature and fluid pressure conditions control rock deformation and mineralization on geological faults, and hence the distribution of earthquakes1. Typical intraplate continental crust has hydrostatic fluid pressure and a near-surface thermal gradient of 31 ± 15 degrees Celsius per kilometre2, 3. At temperatures above 300–450 degrees Celsius, usually found at depths greater than 10–15 kilometres, the intra-crystalline plasticity of quartz and feldspar relieves stress by aseismic creep and earthquakes are infrequent. Hydrothermal conditions control the stability of mineral phases and hence frictional–mechanical processes associated with earthquake rupture cycles, but there are few temperature and fluid pressure data from active plate-bounding faults. Here we report results from a borehole drilled into the upper part of the Alpine Fault, which is late in its cycle of stress accumulation and expected to rupture in a magnitude 8 earthquake in the coming decades4, 5. The borehole (depth 893 metres) revealed a pore fluid pressure gradient exceeding 9 ± 1 per cent above hydrostatic levels and an average geothermal gradient of 125 ± 55 degrees Celsius per kilometre within the hanging wall of the fault. These extreme hydrothermal conditions result from rapid fault movement, which transports rock and heat from depth, and topographically driven fluid movement that concentrates heat into valleys. Shear heating may occur within the fault but is not required to explain our observations. Our data and models show that highly anomalous fluid pressure and temperature gradients in the upper part of the seismogenic zone can be created by positive feedbacks between processes of fault slip, rock fracturing and alteration, and landscape development at plate-bounding faults.
ISSN: 0028-0836

hal-01685757
https://hal.archives-ouvertes.fr/hal-01685757
DOI : 10.1038/nature22355