Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension

Abstract

Research Article| April 01, 1971 Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension JOHN H STEWART JOHN H STEWART U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN H STEWART U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America Received: 03 Apr 1970 Revision Received: 05 Oct 1970 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1971, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1971) 82 (4): 1019–1044. https://doi.org/10.1130/0016-7606(1971)82[1019:BARSAS]2.0.CO;2 Article history Received: 03 Apr 1970 Revision Received: 05 Oct 1970 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN H STEWART; Basin and Range Structure: A System of Horsts and Grabens Produced by Deep-Seated Extension. GSA Bulletin 1971;; 82 (4): 1019–1044. doi: https://doi.org/10.1130/0016-7606(1971)82[1019:BARSAS]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Basin and Range structure can be interpreted as a system of horsts and grabens produced by the fragmentation of a crustal slab above a plastically extending substratum. According to this view, the extension of the substratum causes the basal part of the slab to be pulled apart along narrow, systematically spaced zones which in turn cause the downdropping of complex horizontal prisms (grabens) in the brittle upper crust. The grabens form valleys at the surface; the intervening areas are horsts, or tilted horsts.Not all geologists have agreed, however, that Basin and Range structure consists of a system of horsts and grabens. Instead, the structure is commonly considered to consist of tilted blocks in which the upslope part of an individual block forms a mountain and the downslope part a valley. Recent detailed studies, including geophysical work, suggest that the horst and graben model may be more generally applicable. Many of the valleys in the Great Basin are bounded on both sides by faults that drop the valley block down; these faults are exposed at the surface or can be inferred from steep gravity gradients indicative of steep faulted subsurface bedrock slopes. Some areas that were thought to represent a typical series of tilted blocks may be a series of highly asymmetrical grabens in which one side of a valley is marked by a master fault and the other side by valleyward tilt. With present knowledge, most, or perhaps all, of the major valleys in the Great Basin can plausibly be considered to be grabens, and most or all of the mountains can be considered to be horsts or tilted horsts.The grabens, and the underlying inferred deep zones of extension that cause them, are systematically distributed in the Great Basin. They are generally north-trending features spaced 15 to 20 mi apart. Locally, the pattern is more complex, and individual grabens divide and trend away from each other at acute or high angles. In a few places, the pattern may even be roughly polygonal. The distribution pattern of the grabens and the related deep zones of extension resemble crack patterns in small-scale tensional systems, and both patterns may be mechanically related. By analogy with the small-scale systems, the areas of generally north-trending and parallel grabens require east-west extension, whereas the areas with a possible polygonal pattern of grabens must extend radially.The geometry of block faulting related to Basin and Range structure requires sizable east-west extension, estimated at about 1.5 mi on the average for each major valley and at about 30 to 60 mi across the entire Great Basin. Most of this extension has taken place in the last 17 m.y., or perhaps even in the last 7 to 11 m.y., indicating a rate of extension in the range of 0.3 to 1.5 cm/yr. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.