Eocene to Recent Normal Faulting and SyntectonicSedimentation, Henderson Creek Quadrangle, Southeast Idaho

Document Type

Presentation

Journal/Book Title/Conference

Geological Society of America Abstracts with Programs

Volume

36

Issue

4

Publisher

Geological Society of America

Publication Date

5-3-2004

First Page

21

Abstract

New geologic mapping (supported by EdMap) in the Henderson Creek 7.5 quadrangle in Oneida County, Southeast Idaho, has identified three Tertiary fault sets, each with associated synextensional deposits, which include the Eocene Wasatch Formation, the Miocene Salt Lake Formation, and Quaternary deposits. The study area lies within the hangingwall of the Miocene Bannock detachment system.

The Wasatch Formation consists of red pebble conglomerate overlain by quartzite-boulder beds, with Ordovician Swan Peak quartzite blocks up to 6 meters in diameter. The formation thickens southward toward an east-west striking fault set. This suggests synextensional deposition in an east-striking Eocene half-graben.

The synextensional Miocene Salt Lake Formation (~11.9 Ma to10.2 Ma) was deposited in a separate shallow basin within the south half of the map area. The lacustrine Cache Valley Member (~10.2-9.3 Ma) was deposited in a widespread, shallow lake, bounded on the south and west by the synextensional Steel Canyon fault. An upper conglomerate (~9.7-9.3 Ma) interfingers with the Cache Valley Member, and represents coarse deposits proximal to the active fault.

The third fault set consists of north-striking, Pliocene to Recent, Basin-and-Range faults, including the Wasatch Fault, which makes a 3-5 kilometer-wide right step at a segment boundary just north of the Idaho-Utah border. Extensional folds within the Salt Lake Formation are interpetreted as results of movement along listric faults of this set. A 7 kilometer-long, north-trending extensional anticline is due to a double rollover above oppositely-dipping listric normal faults. Crestal collapse produced a complex array of discontinuous normal faults in the eastern half of the quadrangle.

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