Chapter 10: Tectonic evolution of the Intermontane System; Basin and Range, Colorado Plateau, and High Lava Plains

Abstract

Strong contrasts in the tectonic evolution of the three principal parts of the Intermontane System (Basin and Range, Colorado Plateaus, and High Lava Plains) are responsible for strong contrasts in crustal structure outlined elsewhere in this volume. Extremes in Cordilleran history are represented by the interior of the Colorado Plateaus and the Basin and Range province. The plateaus have enigmatically escaped strong deformation and magmatism since Precambrian time, whereas most parts of the Basin and Range have experienced repeated orogenesis, the youngest of which is continental magmatism and extensional deformation with dimensions and magnitudes that may not be exceeded anywhere in the world. Between these extremes lie the High Lava Plains, parts of which appear to be dominated by the passage of a single major pulse of magmatism and rifting that produced crust no older than late Cenozoic age. Numerous crustal-scale tectonic and magmatic events beginning in Archean time and extending into Cenozoic time are chronicled as events having a potential for molding crustal structure. They include protracted Archean and early Proterozoic south-or southwestdirected continental growth or cratonization by sparsely recorded processes of deformation, sedimentation, magmatism, and metamorphism, followed in middle Proterozoic time by epicratonal basin sedimentation and in the late Proterozoic by reshaping of the western continental margin by passive-margin rifting and foundering. Late Paleozoic and early Mesozoic continent-margin collisional events led to the obduction of the Roberts Mountains and Golconda allochthons and accretion of related terranes. A second event of continent-margin truncation and reshaping occurred in early Mesozoic time. It was followed during Mesozoic time by major east-directed subduction of oceanic lithosphere and associated accretions of volcanotectonic terranes to the west margin of the continent. Genetically related magmatism, metamorphism, and compressional tectonism reached far inboard of the continental margin; these were guided to some extent by preexisting tectonic features. During Cenozoic time, igneous activity of colossal magnitude swept through the Cordillera along regular paths without apparent regard for preexisting tectonic features. Coeval and subsequent extensional tectonism teamed with the magmatism to reshape the geophysical framework of much of the Basin and Range and High Lava Plains. Accordingly, it is a major challenge to recognize the fingerprint of ancient major crustal-scale events within the current geophysical framework.

Cenozoic transverse zones and igneous belts in the Great Basin, Western United States: Their tectonic and economic implications

“…This pattern of migration of magmatism ( Fig. 7) is one of several proposed for the western United States (Anderson, 1989;Best et al, 1989b). In an effort to explain the strong discordance between the orientation of the subduction zone and the igneous belts and their migratory patterns, a progressive steepening or lateral foundering (first in the north, then progressing southward) of the subducted slab was proposed (Lipman, 1980(Lipman, , 1992Best and Christiansen, 1991).…”

“…An important aspect of igneous belts in the Great Basin is that their southward migration was accompanied by generally north-striking normal faults (Anderson, 1989;Armstrong and Ward, 1991;Seedorff, 1991;Gans et al, 1989;Dilles and Gans, 1995;Scott et al, 1995b). Thus, the western end of the Pioche-Marysvale igneous belt (Fig.…”

Application of structural geology to mineral and energy resources of the Central and Western United States

“…These Neogene faults are known as basin-range faults and are generally younger than about 10 Ma (Anderson and others, 1983). They may have formed under an extension direction (with least principal stress oriented west-northwest) that had been rotated clockwise about 60° from the Miocene extension direction (with least principal stress oriented westsouthwest) (Anderson and Ekren, 1977;Zoback and others, 1981;Anderson and others, 1983;Anderson, 1989). Near the Chief Mining District, most basin-range faults strike north, such as those in the Panaca Basin (fig.…”

An integrated geophysical imaging of the upper-crustal features in the Harney Basin, southeast Oregon

“…In the HLP, the time-transgressive Cenozoic volcanic activity covered the area with lava fl ows and pyroclastic material (e.g., Camp and Ross, 2004;Brueseke et al, 2007;Streck and Grunder, 2008), making it diffi cult to identify older crustal structures and decipher tectonic events (Anderson, 1989). Thus, the HLP was the focus of a large project funded by the National Science Foundation, which involved a wide range of geophysical and geological studies that helped resolve the crustal structure of the crust and upper mantle (e.g., Roth et al, 2008;West et al, 2009;Eagar et al, 2010Eagar et al, , 2011Druken et al, 2011;Cox et al, 2013).…”