Lyell Collection
Geological Society, London, Special Publications
Lyell Centre  |   Lyell Collection  |   Subscriptions   |   Geological Society  |   Email alerts  |   Online bookshop  |   Help

Keywords:
Author:
Advanced search>>
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hamilton, W.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Geological Society, London, Special Publications; 1987; v. 28; p. 155-176;
DOI: 10.1144/GSL.SP.1987.028.01.12
© 1987 Geological Society of London

Extension in the Basin and Range Province and East Pacific Margin

Crustal extension in the Basin and Range Province, southwestern United States

W. Hamilton

Branch of Geophysics, US Geological Survey, Denver, Colorado 80225, USA

Cenozoic extension of areally varying ages and amounts has on average doubled the width of the Basin and Range Province. Extensional structures that formed at all depths down to 20 km, and which range in age from Oligocene to Holocene, are widely exposed and are here interpreted in terms of a model of depth-varying deformation. The middle crust is extended by discontinuous ductile shear as internally underformed lenses slide apart along gently dipping zones of mylonite. The tops of these lenses are undulating detachment faults, the composite area of which increases with time as deep lenses slide out from underneath shallower ones. Brittle blocks of upper-crust bedrock above the detachments respond first by rotating between range-front faults, the same direction of rotation being maintained across a series of lenses, and then by pulling completely apart, while basinal strata fill the gaps and are dragged directly on detachment faults. Some faults rise gently from the main detachment zones and surface as range-front faults. Most tilted-block ranges are isolated atop detachments.

Detachment faults cut out crust. Beneath them are mid-crustal rocks of any age and type and above them are mostly upper-crustal rocks, including extensive syndeformational basin sediments rotated to steep or moderate dips. As attenuation proceeds and components rise, detachment faults evolve from ductile to brittle, develop splays, and are themselves broken by steep brittle structures related to new, deeper detachments. Parts of detachment faults remain active even after exposure at the surface, but slip on them is then limited to the down-dip direction. It is inferred from seismic reflection profiles and rock-mechanic considerations that the unexposed lower crust is extended by more pervasive ductile flattening.





This article has been cited by other articles:


Home page
 Geological Society, London, Special PublicationsHome page
T. Odinsen, P. Christiansson, R. H. Gabrielsen, J. I. Faleide, and A. M. Berge
The geometries and deep structure of the northern North Sea rift system
Geological Society, London, Special Publications, 2000; 167: 41 - 57.
[Abstract] [PDF]

Home page
 Geological Society, London, Special PublicationsHome page
R. K. Dokka, T. M. Ross, and G. Lu
The Trans Mojave-Sierran shear zone and its role in Early Miocene collapse of southwestern North America
Geological Society, London, Special Publications, 1998; 135: 183 - 202.
[Abstract] [PDF]