MULTIPLE LINES OF EVIDENCE SUGGEST 30-35 KM OF OFFSET ON THE BLYTHE BASIN STRIKE-SLIP FAULTS: PART OF THE MISSING DEXTRAL SHEAR ACROSS THE MIOCENE PACIFIC-NORTH AMERICA PLATE BOUNDARY?

2020 ◽  
Author(s):  
Paul J. Umhoefer ◽  
◽  
Skyler P. Mavor ◽  
V.E. Langenheim ◽  
L. Sue Beard ◽  
...  
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Strike Slip ◽  
Dextral Shear ◽  
Lines Of Evidence

scholarly journals Extreme Quaternary plate boundary exhumation and strike slip localized along the southern Fairweather fault, Alaska, USA

Geology ◽  
2021 ◽  
Vol 49 (5) ◽  
pp. 602-606 ◽  
Author(s):  
Richard O. Lease ◽  
Peter J. Haeussler ◽  
Robert C. Witter ◽  
Daniel F. Stockli ◽  
Adrian M. Bender ◽  
...  
Keyword(s):  
North America ◽  
Sedimentary Cover ◽  
Plate Boundary ◽  
Slip Rate ◽  
Strike Slip ◽  
Plate Motion ◽  
The North ◽  
Exhumation Rates ◽  
Restraining Bend

Abstract The Fairweather fault (southeastern Alaska, USA) is Earth’s fastest-slipping intracontinental strike-slip fault, but its long-term role in localizing Yakutat–(Pacific–)North America plate motion is poorly constrained. This plate boundary fault transitions northward from pure strike slip to transpression where it comes onshore and undergoes a <25°, 30-km-long restraining double bend. To the east, apatite (U-Th)/He (AHe) ages indicate that North America exhumation rates increase stepwise from ∼0.7 to 1.7 km/m.y. across the bend. In contrast, to the west, AHe age-depth data indicate that extremely rapid 5–10 km/m.y. Yakutat exhumation rates are localized within the bend. Further northwest, Yakutat AHe and zircon (U-Th)/He (ZHe) ages gradually increase from 0.3 to 2.6 Ma over 150 km and depict an interval of extremely rapid >6–8 km/m.y. exhumation rates that increases in age away from the bend. We interpret this migration of rapid, transient exhumation to reflect prolonged advection of the Cenozoic–Cretaceous sedimentary cover of the eastern Yakutat microplate through a stationary restraining bend along the edge of the North America plate. Yakutat cooling ages imply a long-term strike-slip rate (54 ± 6 km/m.y.) that mimics the millennial (53 ± 5 m/k.y.) and decadal (46 mm/yr) rates. Fairweather fault slip can account for all Pacific–North America relative plate motion throughout Quaternary time and indicates stability of highly localized plate boundary strike slip on a single fault where extreme rock uplift rates are persistently localized within a restraining bend.

scholarly journals Distributed Neogene faulting across the western to central Arizona metamorphic core complex belt: Synextensional constriction and superposition of the Pacific–North America plate boundary on the southern Basin and Range

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1409-1435 ◽  
Author(s):  
John S. Singleton ◽  
Nikki M. Seymour ◽  
Stephen J. Reynolds ◽  
Terence Vomocil ◽  
Martin S. Wong
Keyword(s):  
North America ◽  
Plate Boundary ◽  
Detachment Fault ◽  
Normal Faults ◽  
Core Complex ◽  
The Pacific ◽  
Complex Development ◽  
Dextral Shear ◽  
Extension Direction ◽  
Central Arizona

Abstract We present fault data from a belt of Miocene metamorphic core complexes in western and central Arizona (USA) to determine patterns of brittle strain during and after large-magnitude extension, and to evaluate the magnitude of postextensional dextral shear across the region. In the White Tank Mountains, coeval WNW- to NW-striking dextral, normal, and oblique dextral-normal faults accommodated constrictional strain with extension subparallel to the direction of ductile stretching during core complex development. Northwest-striking oblique dextral-normal faults locally accommodated similar strain in the Harquahala Mountains, whereas in the South Mountains, constriction was primarily partitioned on NE-dipping normal faults and conjugate NW- and north-striking strike-slip faults. We interpret brittle constrictional strain to have developed during the late stages of large-magnitude extension associated with core complex development and folding of detachment fault corrugations. The oblique orientation of the Arizona core complex belt with respect to the extension direction likely resulted in a minor component of dextral transtension, accounting for much of the constrictional strain. In addition, far-field stresses associated with the transtensional Pacific–North America plate boundary may have contributed to constriction, which characterizes most Neogene detachment fault systems in the southwest Cordillera. Following cessation of detachment fault slip across the Arizona core complex belt (ca. 14–12 Ma), distributed NW-striking dextral and oblique dextral–NE-side-up (reverse) faults modified the topographic envelope of corrugations to an orientation clockwise of the core complex extension direction. Based on our analysis of this misalignment, we interpret the postdetachment fault dextral shear strain to increase northwestward from 0.03 across the South Mountains (0.5–0.6 km total slip across 18 km) to >0.03–0.07 across the Harquahala and Harcuvar Mountains (1.2–2.5 km of total slip across ∼35 km) and ∼0.2 across the Buckskin-Rawhide Mountains (7–8 km across 36 km). This along-strike variation in dextral shear is consistent with the regional pattern of distributed strain associated with the Pacific–North America plate boundary, as cumulative dextral offset in the lower Colorado River region increases toward the eastern Mojave Desert region to the northwest.

Newly identified strike-slip plate boundary in the northeastern Arabian Sea

Geology ◽  
2000 ◽  
Vol 28 (4) ◽  
pp. 355 ◽  
Author(s):  
Nina Kukowski ◽  
Thies Schillhorn ◽  
Ernst R. Flueh ◽  
Katrin Huhn
Keyword(s):  
Arabian Sea ◽  
Plate Boundary ◽  
Strike Slip

Collective Burial in Late Prehistoric Virginia: Excavation and Analysis of the Rapidan Mound

2003 ◽  
Vol 68 (1) ◽  
pp. 109-128 ◽  
Author(s):  
Gary H. Dunham ◽  
Debra L. Gold ◽  
Jeffrey L. Hantman
Keyword(s):  
Eighteenth Century ◽  
North America ◽  
Historical Context ◽  
Late Prehistoric ◽  
Mortuary Ritual ◽  
New Information ◽  
Virginia Piedmont ◽  
Burial Mounds ◽  
Secondary Burial ◽  
Lines Of Evidence

Recent excavation and analysis of the remaining section of the endangered Rapidan Mound site (44OR1) in the central Virginia Piedmont provide new insights into a unique complex of burial mounds in the Virginia interior. Known since Thomas Jefferson's eighteenth-century description, the mounds are both earth and stone and accretional earthen mounds. Thirteen are recorded, all dating to the late prehistoric and early contact era (ca. A.D. 900-1700). Typically containing few artifacts, the accretional mounds are unusual in North America in the numbers of individuals interred, more than one thousand in at least two cases, and in the nature of the secondary, collective burial ritual that built up the mounds over centuries. Following a review of the characteristics of the mound complex, we focus on the Rapidan Mound and the analysis of the collective, secondary burial features in the mound. Precise provenience information and bioarchaeological analyses of two large and intact collective burial features provide new information on health and diet, and several lines of evidence for demographic reconstruction. Finally, we discuss the mortuary ritual conducted at the mounds within the cultural and historical context of the region.

Sign in / Sign up

Export Citation Format

Share Document