North-south–directed extension, timing of extension, and vertical-axis rotation of the southwest Cady Mountains, Mojave Desert, California

Ross, Timothy M.

doi:10.1130/0016-7606(1995)107<0793:nsdeto>2.3.co;2

Cited by 7 publications

(11 citation statements)

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“…Finally, Ross's (1995) study of the western Cady Mountains is consistent with an original north-south orientation of extension in that local area but does not require it. Ross found large clockwise declination anomalies in Miocene strata.…”

Section: Extension Directionsupporting

confidence: 63%

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Cenozoic evolution of the Mojave block of southern California

Glazner¹,

Walker

Bartley

et al. 2002

Geologic Evolution of the Mojave Desert and Southwestern Basin and Range

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The recorded Cenozoic history of the Mojave Desert region of southern California began in the latest Oligocene, when intense volcanism and tectonism interrupted a long early Tertiary silence. Volcanism commenced across the region in an east-west band ca. 24-22 Ma. Northwest of Barstow, volcanism was accompanied by intense crustal extension and development of a metamorphic core complex. Outside of this relatively restricted area, extension was minor or absent. After extension ceased ca. 18 Ma, volcanism shifted to small-volume eruptions of basalt. Post-extensional deformation has largely been by strike-slip faulting along northwest-striking dextral faults and west-striking sinistral faults, and total dextral slip across the Mojave Desert region since the early Miocene is ϳ45-60 km. Strike-slip deformation has been overprinted locally by intense north-south contraction that is the dominant style of deformation in the western Mojave block.Paleomagnetic data indicate that parts of the Mojave block were rotated clockwise, although the magnitude and timing of this rotation are poorly determined. The best evidence for large (Ͼ45Њ) rotation comes from the area east of Barstow, where large clockwise declination anomalies and Mesozoic and Cenozoic dikes with anomalous strikes may reflect early Miocene clockwise deflection along the Mojave River fault.Volcanism and tectonism in the Mojave block resulted from interactions among the North American, Pacific, and various oceanic plates. Patterns of volcanism and tectonism do not correlate with growth of slab windows beneath the continent, but do correlate with the position of the subducted Mendocino fracture zone. Plate-circuit reconstructions suggest that the driving force for extension was divergence between the Pacific and North American plates along the transform margin that separated the two. This hypothesis accounts for the direction, magnitude, and rate of extension in the Mojave block.

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Section: Extension Directionsupporting

confidence: 63%

“…However, Dokka (1989) and Ross (1995) interpreted paleomagnetic data to indicate that extension originally occurred with the hanging wall moving to the north and that the current northeast orientation of extension vectors results from clockwise rotation. We view this interpretation as unlikely for several reasons.…”

Section: Extension Directionmentioning

confidence: 92%

Cenozoic evolution of the Mojave block of southern California

Glazner¹,

Walker

Bartley

et al. 2002

Geologic Evolution of the Mojave Desert and Southwestern Basin and Range

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“…1) underwent ~21° of clockwise rotation about vertical axes subsequent to its deposition (~16 Ma). Ross (1992Ross ( , 1995, Ross et al (1991), and Dokka et al (1991) indicated that the area west of the type Hector Formation outcrops underwent a total clockwise rotation of ~130°± 13° about vertical axes (Fig. 1, southwest Cady Mountains).…”

Section: Geologic Overview and Previous Workmentioning

confidence: 94%

“…In this chapter, taxa of late Arikareean age are recognized in the northern Cady Mountains and occur stratigraphically ~21 m (70 ft) below the 19-to 20-m.y.-old basalt. In terms of regional correlations (e.g., Woodburne and Swisher, 1995;this chapter) Miller (1980); central Cady Mountains after Williamson (1980); southwestern Cady Mountains after Ross (1995); type Hector Formation after Woodburne et al (1974); southeastern Cady Mountains after Glazner (1988 Woodburne and Swisher (1995). area, the Hector Formation of the northern Cady Mountains holds the potential of being a calibrated sequence containing the Arikareean/Hemingfordian boundary in North America.…”

Section: Geologic Overview and Previous Workmentioning

confidence: 98%

Arikareean and Hemingfordian faunas of the Cady Mountains, Mojave Desert Province, California

Woodburne¹

1998

Depositional Environments, Lithostratigraphy, and Biostratigraphy of the White River and Arikaree Groups (Late Eocene to Early

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The Mojave Desert of southern California contains a number of basins that preserve mammal-bearing sediments, and intercalated volcanic tuffs, of late Oligocene to Miocene age. Of these, only the Cady Mountains preserve well-studied sections with mammal fossils of Arikareean to early and late Hemingfordian age. This report is an update of geochronologic and faunal information contained in these strata, known as the Hector Formation. With that accomplished, these radioisotopic and faunal data aid in assessing the age of presumptively correlative first appearance datum (FAD) of taxa in the type sequences of Nebraska.The Black Butte Mine and Logan Mine Local Faunas are found in superposition in the Hector Formation on the southwestern flank of the Cady Mountains. The two assemblages appear to best correlate with taxa of late Arikareean age elsewhere and are calibrated by a K-Ar age of ~21.6 Ma found stratigraphically near the upper part of the Black Butte Mine sequence. Black Butte Mine taxa important for regional correlation include Merychyus calaminthus and Stenomylus cf. hitchcocki of late Arikareean (Ar3) age, with Merychyus having a lowest stratigraphic datum (LSD) in the Harrison Formation of Nebraska. In the Cady Mountains, M. calaminthus is bracketed by tuffs dated at 22.9 and 21.6 Ma, suggesting that the coeval part of the Harrison Formation is ~22 Ma old. Temporally significant taxa in the Logan Mine Local Fauna include Michenia cf. M. agatensis and Ustatochoerus cf. leptoscelos (Ar4). Michenia (including M. agatensis) has a lowest stratigraphic datum (LSD) in the Marsland Formation in Nebraska (Upper Harrison beds, as restricted by Hunt, 1985, 1990) dated at ~19.2 Ma. The deposits that bear the Logan Mine Local Fauna include lithic fragments eroded from the Peach Springs Tuff dated at 18.5 ± 0.2 Ma. An LSD of Michenia cf. agatensis below the Peach Springs Tuff clasts in the Hector Formation is similar to the LSD of that taxon in the late Arikareean (Ar4) fauna of the Upper Harrison beds of Nebraska. An LSD of Ustatochoerus cf. leptoscelos of the Logan Mine Local Fauna just above the Peach Springs Tuff clasts correlates to an early Hemingfordian (He1) age in Nebraska (taxa in the Runningwater Formation). Whereas the Black Butte Mine and most of the Logan Mine taxa are consistent with correlations to Ar3 and Ar4, some Logan Mine faunal elements thus range into He1 in the mammalian biochronological hierarchy. The Logan Mine Local Fauna nevertheless records the Arikareean/Hemingfordian boundary in the Mojave Desert Province of California, interpolated at ~18.8 m.y. as bracketed between clasts of the 18.5-Ma-old Peach Springs Tuff (above) and by a basalt considered on paleomagnetic grounds as being 19 to 20 m.y. old (below) in the Northern Cady Mountains. Woodburne, M. O.

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“…Remanent magnetization may be important for some of the Cenozoic volcanic rocks (MacConnell and others, 1994;Ross, 1995;Schermer and others, 1996) but is not anticipated to affect magnetic anomalies arising from the pre-Cenozoic crystalline basement rocks. The asymmetry is caused by the nonvertical main magnetic field and thus is a function of magnetic latitude.…”

Section: Reduction To Polementioning

confidence: 99%

Aeromagnetic data, processing, and maps of Fort Irwin and vicinity, California

Langenheim¹,

Jachens²

2014

Open-File Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS (1-888-275-8747) For an overview of USGS information products, including maps, imagery, and publications, visit http: //www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Langenheim, V.E., and Jachens, R.C., 2014, Aeromagnetic data, processing, and maps of Fort Irwin and vicinity, California, chap. I of Buesch, D.C., ed., Geology and geophysics applied to groundwater hydrology at Fort Irwin, California: U. AbstractAeromagnetic data help provide the underpinnings of a hydrogeologic framework for Fort Irwin by locating inferred structural features or grain that influence groundwater flow. Magnetization boundaries defined by horizontal-gradient analyses coincide locally with Cenozoic faults and can be used to extend these faults beneath cover. These boundaries also highlight the structural grain within the crystalline rocks and may serve as a proxy for fracturing, an important source of permeability within the generally impermeable basement rocks, thus mapping potential groundwater pathways through and along the mountain ranges in the study area.

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North-south–directed extension, timing of extension, and vertical-axis rotation of the southwest Cady Mountains, Mojave Desert, California

Cited by 7 publications

References 0 publications

Cenozoic evolution of the Mojave block of southern California

Cenozoic evolution of the Mojave block of southern California

Arikareean and Hemingfordian faunas of the Cady Mountains, Mojave Desert Province, California

Aeromagnetic data, processing, and maps of Fort Irwin and vicinity, California

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