Pre-Mesozoic geology of Huizachal-Peregrina Anticlinorium, Ciudad Victoria, Tamaulipas, and adjacent parts of eastern Mexico

The Huizachal-Peregrina Anticlinorium is a large NNW-trending structure in the front ranges of the Sierra Madre Oriental of Mexico (23° 45ʹ N; 99° 10ʹ W). The breached core of the anticlinorium exposes three major geologic terranes: (1) . A late Precambrian granulite terrane (Novillo Gneiss) remarkably similar in composition, appearance, grade and age of metamorphism to rocks of the Grenville Province, especially the Adirondacks; (2). A mid-Paleozoic low-grade metamorphic complex (Granjeno Schist) of volcano-sedimentary origin with ophiolite rock assemblages, that resemble rocks of the Ouachita-Appalachian inner zones; and (3). A strongly folded and faulted section of Paleozoic fossilifireous sedimentary strata, more than 1500 m thick, similar to the rocks of the Ouachita frontal zone exposed in the Marathon region of Texas. Except for an extensive subcrop terrain of Permo-Triassic granitic intrusives, the terranes in the area studied represent "unique samples" of the Pre-Mesozoic basement framework of eastern Mexico. These terranes belong to two ancient superposed orogenic systems: the Late Precambrian Oaxacan (Grenville) and the Paleozoic Huastecan (Ouachita-Appalachian) structural belts. Based on the geologic study of these pre-Mesozoic terranes at Huizachal-Peregrina, and compared with the widely spaced and limited outcrops (and sub-crops) of equivalent rock units of eastern Mexico, a tectonic model is proposed which interprets the granulite terrane as representative of continental crust, and the low-grade metamorphic terrane as rocks that accumulated on top of the ocean crust of a marginal basin. This latter sequence experienced a complex history of deformation and metamorphism as it was subducted towards the east, culminating 330 m.y. ago. The onset of Carboniferous-Permian orogenic flysch sedimentation is interpreted to have occurred when the marginal basin became closed by an arc-continent collision. The Permo-Triassic granitic rock terrane of the subsurface of the Gulf Coastal Plain represents the magmatic roots of that volcanic arc. The pervasive NW to NNW-trending structural grain, of the Oaxacan and Huastecan structural belts south of Huizachal-Peregrina through Oaxaca, when compared to the NE-trending distribution of Precambrian and Paleozoic terranes in the United States are compatible with the existence of a proposed zone of large left-lateral displacement across northern Mexico.