The Juchatengo complex: an upper-level ophiolite assemblage of late Paleozoic age in Oaxaca,southern Mexico     

Grajales-Nishimura  José Manuel  Ramos-Arias  Mario Alfredo  Solari  Luigi  Murillo-Muñetón  Gustavo  Centeno-García  Elena  Schaaf  Peter  Torres-Vargas  Ricardo 《International Journal of Earth Sciences》2018,107(3):1005-1031

International Journal of Earth Sciences - The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated...  相似文献   

Palaeomagnetism of the Guaniguanico Cordillera, western Cuba: a pilot study     

L. M. Alva-Valdivia  A. Goguitchaichvili  J. Cobiella-Reguera  J. Urrutia-Fucugauchi  M. Fundora-Granda  J. M. Grajales-Nishimura  C. Rosales 《Cretaceous Research》2001,22(6):705

A palaeo- and rock-magnetic study was carried out on the Jurassic–Cretaceous Guaniguanico Cordillera (15 sites, 112 oriented cores) in order to define a preliminary magnetostratigraphy and to obtain some constraints on the tectonic evolution of western Cuba. Rock-magnetic experiments indicate Ti-poor titanomagnetites as principal remanence carriers. Two magnetic phases seem to be present in a few samples: some spinels, which saturate at moderate magnetic fields and goethite, with higher coercivity. The presence of hematite (or mixture of spinels and hematite) is apparent in two units. In most cases the characteristic palaeodirections could be determined above 300°C. Eleven sites yield normal magnetic polarity and four reverse. The polarity zones can be tentatively correlated to chrons CM29–C24 in the reference geomagnetic polarity time scale. The mean palaeodirection calculated from all sites is Dm=335.7°, Im=43.1°, K=11, α₉₅=12.3 and N=15. The corresponding palaeopole is Plat=66.4°, Plong=205.8°, K=13, and A₉₅=11.1. This pole is not significantly different from North American Jurassic–Cretaceous poles. This suggests that no major latitudinal displacements and deformation have occurred since the Jurassic, in contrast to some previously proposed tectonic models.  相似文献   

Effects of Physical Processes and Sampling Resolution on Fault Displacement Versus Length Scaling: The Case of the Cantarell Complex Oilfield,Gulf of Mexico     

Shunshan Xu  Angel F. Nieto-Samaniego  Gustavo Murillo-Muñetón  Susana A. Alaniz-Álvarez  José M. Grajales-Nishimura  Luis G. Velasquillo-Martinez 《Pure and Applied Geophysics》2016,173(4):1125-1142

  相似文献   

Geochemistry of paleozoic basalts from the Juchatengo complex of southern Mexico: tectonic implications     

J. M. Grajales-Nishimura  E. Centeno-Garcia  J. D. Keppie  J. Dostal 《Journal of South American Earth Sciences》1999,12(6):135

Analyses of Lower Permian or older basalts and associated dykes of the Juchatengo sequence indicate that they are rift tholeiites that formed in a continental rift or back-arc tectonic setting. Age constraints include a Middle Permian fossil recovered from the tectonically overlying sediments and a cross-cutting, post-tectonic pluton dated by K/Ar on hornblende at 282±6 Ma. A location adjacent to the Oaxacan Complex or other old continental crust is suggested by (1) an Nd_i isotopic value of −8.95 and a T_DM age of 1487 Ma in the overlying sediments, which are similar to the Oaxacan Complex; (2) enrichment of incompatible elements in the lavas, suggesting old crustal contamination; and (3) the presence of Permian–Triassic calc-alkaline plutons that stitch the Juchatengo–Oaxaca boundary. The possible tectonic models depend on the age of the Juchatengo basalts, which requires future geochronological work. If the Juchatengo basalts are Permo-Carboniferous, they could have formed near the eastern edge of a back-arc basin: the contemporaneous arc would have rifted away to the west. Eastward migration of the arc magmatism indicated by the Permian–Triassic calc-alkaline plutonism may reflect shallowing of the dip of the subduction zone, which probably also produced the deformation of the Juchatengo sequence.  相似文献   

Changes in fault length distributions due to fault linkage     

Shunshan Xu  A.F. Nieto-Samaniego  S.A. Alaniz-Álvarez  L.G. Velasquillo-Martínez  J.M. Grajales-Nishimura  J. García-Hernández  G. Murillo-Muñetón 《Journal of Geodynamics》2010,49(1):24-30

Fault linkage plays an important role in the growth of faults. In this paper we analyze a published synthetic model to simulate fault linkage. The results of the simulation indicate that fault linkage is the cause of the shallower local slopes on the length–frequency plots. The shallower local slopes lead to two effects. First, the curves of log cumulative number against log length exhibit fluctuating shapes as reported in literature. Second, for a given fault population, the power-law exponents after linkage are negatively related to the linked length scales. Also, we present datasets of fault length measured from four structural maps at the Cantarell oilfield in the southern Gulf of Mexico (offshore Campeche). The results demonstrate that the fault length data, corrected by seismic resolution at the tip fault zone, also exhibit fluctuating curves of log cumulative frequency vs. log length. The steps (shallower slopes) on the curves imply the scale positions of fault linkage. We conclude that fault linkage is the main reason for the fluctuating shapes of log cumulative frequency vs. log length. On the other hand, our data show that the two-tip faults are better for linear analysis between maximum displacement (D) and length (L). Evidently, two-tip faults underwent fewer fault linkages and interactions.  相似文献