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Title: CMS Thrust 1 Summary.

Abstract

Abstract not provided.

Authors:
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1392752
Report Number(s):
SAND2016-8939PE
647298
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the CMS kickoff meeting.
Country of Publication:
United States
Language:
English

Citation Formats

Shulenburger, Luke. CMS Thrust 1 Summary.. United States: N. p., 2016. Web.
Shulenburger, Luke. CMS Thrust 1 Summary.. United States.
Shulenburger, Luke. 2016. "CMS Thrust 1 Summary.". United States. doi:. https://www.osti.gov/servlets/purl/1392752.
@article{osti_1392752,
title = {CMS Thrust 1 Summary.},
author = {Shulenburger, Luke},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Conference:
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  • The basin-range and Sevier tectonic events are well-documented in Clark County, Nevada. Other tectonic events have been interpreted from structural relationships in the Spring Mountains. These include an early thrust-faulting event and a high-angle faulting event that occurred between emplacement of the early thrust and emplacement of the Keystone thrust. The results of this study indicate that there was not an early thrust event nor was there high-angle faulting prior to the Sevier deformational event. The Cottonwood fault and the Contact thrust in the Spring Mountains are interpreted here as a lateral ramp and floor thrust beneath a duplex faultmore » zone. The Keystone thrust forms the roof thrust for the duplex fault zone that bows up the upper plate of the Keystone thrust. The Red Springs thrust is interpreted as the Keystone thrust, which was broken and differentially rotated during Neogene oroclinal bending associated with the Las Vegas shear zone. The structural relationships in the Spring Mountains do not require any Mesozoic or Cenozoic deformational episodes other than the well-known Sevier and basin-range events.« less
  • The total displacement field for any thrust sheet is made up of two independent components: translation along the fault, and internal deformation of the sheet. The internal deformation can be quantified by measuring strain within the sheet. Although strain within external thrust sheets is typically inhomogeneous at the mesoscopic scale, strain does show regular patterns of variation at the scale of the sheet as a whole. The total internal deformation of a sheet can be represented by a deformation profile which has a simple geometric form at the largest scale, based on information available from well studied thrust sheets. Usingmore » such known profiles and compatibility constraints it is possible to minimize the data needed to define the deformation profiles of other sheets. The profiles can be then used to help in unstraining sheets during restoration in cross-section balancing. Based on field observations and the geometric patterns of deformation profiles, most external thrust sheets, including those in the Sevier fold-and-thrust belt (FTB) of ID-UT-WY, show early layer-parallel shortening (LPS) as the most important component of internal deformation. This strain can be removed in a straightforward manner during the last stage of restoration, and significantly affects the geometry of the restored section. In the northern ID-UT-WY FTB salient, the restored basin taper is reduced by 6[degree] to less than 4[degree] for most of the major thrust sheets. Since original basin taper may have important implications for thrust belt evolution, changes in basin taper resulting from strain removal for thrust sheets significantly affects the interpretation of FTB evolution in an area.« less
  • Structural curvature in the northern part of the Wyoming-Idaho thrust belt (WITB) may be the result of either along-strike variations in pre-thrust stratigraphy or a buttress which physically concentrated shortening, or possibly both. Most thrust sheets of the WITB strike northward and were translated eastward, but in the Snake River Range (SRR) (the northernmost range in the WITB), structural strike curves from northward to nearly westward. Structural cross sections of the SRR are generally drawn in a radial pattern creating a volumetric imbalance in regional palinspastic restorations. Stratigraphic separation diagrams of major, through-going thrust faults in the SRR show extensivemore » cut off in upper Paleozoic strata. New measured sections of upper Paleozoic stratigraphy at locations in several major thrust sheets of the WITB and in the foreland, new structural cross sections and mapping, and existing paleomagnetic data are used in a new interpretation of the origin of structural curvature in the WITB. Published paleomagnetic data require counterclockwise rotation of frontal thrust sheets along the northern boundary of the WITB, but no rotation of eastward-translated thrust sheets farther south along most of the WITB. Evidence for both a pre-existing west-trending depositional margin and rotation of frontal thrust sheets suggests that buttressing and modification of structural strike occurred along an oblique ramp where differences in stratigraphic thickness and possible pre-existing fault partitioning of the Paleozoic strata are localized.« less
  • Surface geology is combined with abundant industry seismic-reflection data in the central Bear River Range and Bear Lake Plateau to depict the form and interactions of the Paris-Willard, Laketown-Meade, and Crawford thrust faults. The Paris thrust loses displacement to the south, dying out into splays and a conical fold as displacement is transferred to the Willard thrust. West-southwest of Woodruff, Utah, splays of the Laketown-Meade and Woodruff thrust faults interfinger through extensive footwall imbrication and accommodate a major splay that trends northeast into the Crawford thrust fault, indicating a change in palinspastic thrust vectors. Reorientation of these vectors is possiblemore » due to the imbricate stack of thrusts acting as a pivot while simultaneously accommodating thrust-to-thrust displacement transfer. This thrust ramps lower Paleozoic rocks up to the base of the overlying Tertiary Wasatch Conglomerate. This relationship implies possible reactivation and incorporation of this older thrust into the Crawford thrust fault east of Bear Lake. The sharp bend in the surface trace of the Crawford normal fault southeast of Randolph, Utah reflects the separation of the Crawford thrust and this splay. Cross-sections indicate a major splay off the basal decollement in the Crawford thrust sheet that accommodated displacement during the transition from thrusting on the western thrust system to the structurally lower eastern thrust system. This thrust folds the Laketown-Meade thrust in the central Bear River Range and trends northeast where it forms a series of hanging-wall anticlines that have been extensively targeted for hydrocarbon exploration.« less
  • Cross sections of the northwest Montana thrust belt, constructed principally from published geologic maps and a number of cross-strike traverses, provide constraints on the geometry and sequential evolution of thrust systems, which in turn are compatible with the critical-wedge model of thrust-belt mechanics. Sequential restorations of Sawtooth Range thrust systems, in map and cross section, indicate that earlier formed thrusts to the west remained active during the eastern advance of the thrust front. Three-dimensional balancing arguments likewise suggest that the Lewis thrust, to the north and west, continued to move during the development of the Sawtooth Range. Continuous or periodicallymore » reactivated motion on the Lewis was responsible for the maintenance of critical taper in the northern and western Sawtooth Range, the footwall Paleozoic were strengthened by the overlying sheet and experienced little internal imbrication. However, where the thrust front advanced in front of the leading edge of the Lewis, the thinly-tapered Paleozoic package was imbricated to from the characteristic sawtooth-shaped ranges of the Montana thrust belt. Thus, critical taper in the Sawtooths was maintained by duplexing of Paleozoic rocks and back-rotation accompanying piggy-back thrusting. Additional duplexes of Paleozoic rocks in the footwall of the Lewis may have developed late in the orogeny to compensate for erosion of the overlying Lewis sheet. Continuing motion on the Lewis, as it was folded over footwall duplexes, produced out-of-sequence imbricates within the Lewis sheet.« less