+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Rapid changes of stress-field in the passive continental margin of southeastern Brazil

, : Rapid changes of stress-field in the passive continental margin of southeastern Brazil. Congres Geologique International, Resumes 33

Cenozoic reactivations of NE to E-W-oriented Neoproterozoic shear zones and associated sedimentation in continental rift basins offer a unique opportunity to study the changes of stress-field in the passive continental margin of southeastern Brazil. Inversion of striae from Paleogene-Neogene faults shows different stress regimes which varies with time. Continental rifting occurred during the Eocene-Oligocene with reactivation of NE to E-W-oriented shear zones as normal faults under NNW-SSE-oriented extension, the deposition of alluvial and lacustrine deposits and extrusion of ankaramite lava-flows. After its installation and syntectonic deposition the rift system was subjected to four phases of deformation. Basin inversion initiated in the early Miocene with left-lateral strike-slip and minor thrust reactivation of NE to E-W shear zones, under a general strike-slip regime with NW-SE extension and local NE-SW compression. Structural highs related to transpression caused the inversion and segmentation of the rift basins. Deposition of fluvial sediments in pull-apart basins took place during the transtension or final relaxation of the compressive stress related to this tectonic phase. Late Miocene fluvial meandering deposits as well as late Pleistocene paleosols, colluvium and stone-line deposits record the second phase of deformation, as right-lateral strike-slip and thrust reactivation of NE to E-W-oriented Neoproterozoic shear zones, as result of a NW-SE compression and NE-SW extension, which occurred during the late Pleistocene-Holocene. During the Holocene the stress regime changed to an E-W to WNW-ESE extension locally responsible for the generation of N-S-trending grabens with syntectonic colluvial and alluvial deposition. The last change of stress field is recorded by an E-W direction of compression which generated E-W normal and N-S reverse faults, and widespread families of ENE-NE and WNW-NW hybrid and shear joints affecting colluvial and alluvial deposits younger than 3,410 yr BP. The rapid variation of stress field in this sector of the passive continental margin of southeastern Brazil may be regionally related to the interplay between the ridge-push and slab-pull of South American plate with respect to the Nazca and African plates, respectively, and the influence of intraplate local stress related to the elevated topography of the continental margin, the loading of the thick sedimentary wedges in the adjoining Santos and Campos basins, and perhaps the sea-level rising after the late Pleistocene glaciation. (Financial support by FAPESP, grant 03/08031-0 and CNPq, grant 304649/2005-8).


Other references

Browne J.H., 1986: Members of the malvaceae family rare in north western victoria australia. Victorian Naturalist (blackburn): 150-157

Tsukamura, M.; Mizuno, S.; Murata, H., 1981: Occurrence of Mycobacterium tuberculosis and strains of the Mycobacterium avium-M. intracellulare complex together in the sputum of patients with pulmonary tuberculosis. Out of 97 strains of M. tuberculosis isolated from the sputum of the same number of patients, 11 were shown to consist of a mixed population of M. tuberculosis and a strain of the M. avium-M. intracellulare (MAI) complex. The most effective method...

Dewilde,; Houston, A.H., 1967: Hematological aspects of the thermoacclimatory process in the rainbow trout, Salmo gairdneri. The blood oxygen capacity of the rainbow trout has been investigated as a function of thermal acclimation in terms of erythrocyte abundance, packed cell volume, hemoglobin concentrations, and mean erythrocytic volume and hemoglobin content. Fish a...

Fleming, J.A., 1947: The international scientific unions. Proceedings of the American Philosophical Society 91(1): 121-125

Manupella G.; Balaco Moreira J.C.; Oliveira V., 1994: Dolomites of the Sousel-Estremoz-Alandroal area. The target area of this study is situated in the Sub-Zone of Estremoz-Barrancos included in the SW segment of the Hercinica Chain, more specifically in the Ossa-Morena Zone. It corresponds to an anticlinal structure of the second orogenic phase wi...

Geele G.; Garrett E.; Hageman J.H., 1975: Effect of benzene boronic acids on sporulation and on production of serine proteases in bacillus subtilis cells. Gerhardt, Philipp, Ralph N Costilow And Harold L Sadoff (Ed ) Spores Vi Sixth International Conference East Lansing, Mich , U S A , Oct 10-13, 1974 Xiii+619p Illus American Society For Microbiology: Washington, D C , U S A Isbn 0-914826-03-4 391-396

Smith, R.A.; Sisk, R.; Lockhart, P.; Mathewes, S.; Gilbert, T.; Walker, K.; Piggot, J., 1993: Isolation of glucagon antagonists by random molecular mutagenesis and screening. Glucagon has an important role in the regulation of glucose homeostasis, and glucagon antagonists may be effective therapeutic agents in the control of diabetes mellitus. We were able to identify a number of analogs with antagonist activity by cre...

Mohamed, A.; Rayas Duarte, P., 1994: Characterization of carbohydrates in L albus. Cereal Foods World 39(8): 613

Meyer, Walter G., 1949: Corn proteins now utilized to make glutamate. Process has been developed for the use of by-products of the wet-milling corn industry for the production of glutamate. Hydrolysis of corn protein by concentrated HC1 for 15-20 hrs. at atmospheric pressure. The resultant hydrolysate is diluted pre...

Booker J.A.; Johnston M.; Tydd T.; Booker C.I.; Mitchell R., 1985: Mortality from upper gastrointestinal hemorrhage in the elderly a statistical analysis of predictors of continued or rebleeding and death. Australian & New Zealand Journal of Medicine 15(1 SUPPL 1): 197