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Title: Late Ordovician paleogeography of central Idaho and its tectonic implications

Abstract

The Late Ordovician (Cincinnatian, Ashgill) paleogeography of central Idaho has been weakly constrained in the past. Previously, this area was treated as a simple extension of the miogeocline-eugeocline paleogeography defined from units in the Great Basin (Nevada and Utah). Detailed analysis of the Upper Ordovician Fish Haven Dolomite enables a more refined paleogeographic interpretation to be made at this time. The Fish Haven Dolomite (260 m or 800 ft, average thickness) of central Idaho is composed of 16 different carbonate facies which can be grouped into three sequences; facies within each sequence are depositionally related. Overall, the facies and sequences indicate that a carbonate ramp formed in central Idaho outboard of the craton and a hinge zone, within a subsiding area of the miogeocline. Shallow subtidal ramp deposits were probably deposited in approximately 30 m (100 ft.), or less, of water depth. During this time interval, open ocean, anoxic bottom waters extended up into deep ;subtidal regions (60 m or 200 ft). This information indicates that the Late Ordovician carbonate ramp underwent backstepping at its outermost portion resulting n drowning of the western ramp and eventual migration of transitional facies deposits (Roberts Mountains Formation) over miogeoclinal deposits. Tectonics played anmore » active part in the deposition of the Fish Haven Dolomite in the miogeocline of central Idaho. The ultimate cause of the tectonism is not known at this time, but could be related to changes in the rate of sea-floor spreading, active structures within the continental margin, proximity of the Ordovician Klamath Mountains island arc Terrane, or unknown processes.« less

Authors:
 [1]
  1. Univ. of Idaho, Moscow (United States)
Publication Date:
OSTI Identifier:
5171174
Report Number(s):
CONF-9103128-
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Journal Name:
AAPG Bulletin (American Association of Petroleum Geologists); (United States)
Additional Journal Information:
Journal Volume: 75:2; Conference: American Association of Petroleum Geologists (AAPG)/Society of Economics, Paleontolgists, and Mineralogists (SEPM)/Society of Exploration Geophysicists (SEG)/Society of Professional Well Log Analysts (SPWLA) Pacific Section annual meeting, Bakersfield, CA (United States), 6-8 Mar 1991; Journal ID: ISSN 0149-1423
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CARBONATE ROCKS; DEPOSITION; IDAHO; SEDIMENTARY BASINS; GEOLOGIC HISTORY; STRATIGRAPHY; TECTONICS; GEOLOGIC FORMATIONS; LITHOLOGY; ORDOVICIAN PERIOD; DEVELOPED COUNTRIES; FEDERAL REGION X; GEOLOGIC AGES; GEOLOGIC STRUCTURES; GEOLOGY; NORTH AMERICA; PALEOZOIC ERA; ROCKS; SEDIMENTARY ROCKS; USA; 580000* - Geosciences

Citation Formats

Measures, E A. Late Ordovician paleogeography of central Idaho and its tectonic implications. United States: N. p., 1991. Web.
Measures, E A. Late Ordovician paleogeography of central Idaho and its tectonic implications. United States.
Measures, E A. 1991. "Late Ordovician paleogeography of central Idaho and its tectonic implications". United States.
@article{osti_5171174,
title = {Late Ordovician paleogeography of central Idaho and its tectonic implications},
author = {Measures, E A},
abstractNote = {The Late Ordovician (Cincinnatian, Ashgill) paleogeography of central Idaho has been weakly constrained in the past. Previously, this area was treated as a simple extension of the miogeocline-eugeocline paleogeography defined from units in the Great Basin (Nevada and Utah). Detailed analysis of the Upper Ordovician Fish Haven Dolomite enables a more refined paleogeographic interpretation to be made at this time. The Fish Haven Dolomite (260 m or 800 ft, average thickness) of central Idaho is composed of 16 different carbonate facies which can be grouped into three sequences; facies within each sequence are depositionally related. Overall, the facies and sequences indicate that a carbonate ramp formed in central Idaho outboard of the craton and a hinge zone, within a subsiding area of the miogeocline. Shallow subtidal ramp deposits were probably deposited in approximately 30 m (100 ft.), or less, of water depth. During this time interval, open ocean, anoxic bottom waters extended up into deep ;subtidal regions (60 m or 200 ft). This information indicates that the Late Ordovician carbonate ramp underwent backstepping at its outermost portion resulting n drowning of the western ramp and eventual migration of transitional facies deposits (Roberts Mountains Formation) over miogeoclinal deposits. Tectonics played an active part in the deposition of the Fish Haven Dolomite in the miogeocline of central Idaho. The ultimate cause of the tectonism is not known at this time, but could be related to changes in the rate of sea-floor spreading, active structures within the continental margin, proximity of the Ordovician Klamath Mountains island arc Terrane, or unknown processes.},
doi = {},
url = {https://www.osti.gov/biblio/5171174}, journal = {AAPG Bulletin (American Association of Petroleum Geologists); (United States)},
issn = {0149-1423},
number = ,
volume = 75:2,
place = {United States},
year = {Fri Feb 01 00:00:00 EST 1991},
month = {Fri Feb 01 00:00:00 EST 1991}
}

Conference:
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