About This Item
- Full TextFull Text(subscription required)
- Pay-Per-View PurchasePay-Per-View
Purchase Options Explain
Share This Item
The AAPG/Datapages Combined Publications Database
Montana Geological Society
Abstract
MTGS-AAPG
1997 Bighorn Basin Symposium Guidebook
July,
Evidence for right-oblique-slip on a northern segment of the Big Trails
fault
system, southern Bighorn Mountains, Wyoming
ABSTRACT
The Big Trails fault
is traditionally defined as a northeast-trending, basement-controlled, high angle
fault
extending nearly
53 miles along the crest of the southern Bighorn Mountains. However, the authors have observed several features along this
fault
typical for strike-slip or oblique-slip
fault
models. The
fault
begins at the intersection of the Owl Creek and the
Casper arch thrusts on the south and terminates on the east-west trending Tensleep
fault
to the north.
In an area mapped by the authors, the main fault
trace is an eighth to a half mile wide, and characterized in map view by
multiple braided
fault
strands. Variable displacement and reversals of displacement occur on the main
fault
trace and on subsidiary
faults. Horizontal to near horizontal slickensides were measured along the
fault
; plunge of the striations ranged from 10-55°
in a predominantly northerly direction. "Horsetail"
fault
splays mapped in the west
fault
block indicate drag from right oblique-slip.
Horst and graben features identified in the
fault
trace correlate with confining and releasing bends and the trace of the
main
fault
is near vertical in profile. Vertical offset, i.e., stratigraphic separation, which is down to the west along the
majority the
fault
, shifts to down to the east near the north end. Separation ranges from almost zero on the north end, where
vertical offset shifts to down to the east, to a maximum of more than 4500 feet near the middle of the
fault
. Horizontal offset
in the form of right-slip is estimated at 2-3 miles.
The Big Trails fault
is basement controlled and coincident with zones of weakness. These zones are defined by northeast trending
quartz diorite, mafic, and amphibolite dikes of early Proterozoic and Archean age. We suggest that the
fault
may continue
north of the Tensleep
fault
and connect with the Crazy Woman "tear"
fault
. The Crazy Woman
fault
forms the southern boundary
of the Sisters Hill segment of the large east verging thrust feature along the eastern flank of the Bighorn Mountains, west
of the town of Buffalo. The Big Trails
fault
is a result of a northeast-southwest oriented horizontal compressional event
in the Rocky Mountain foreland during the Laramide orogeny.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
Protected Document: $10 | |
Internal PDF Document: $14 | |
Open PDF Document: $24 |