- Usage in publication:
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- Helenmode member*
- Modifications:
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- Named
- Dominant lithology:
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- Clay
- Shale
- Sandstone
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Named as a member of Erwin formation. Named for Helenmode pyrite mine near Sadie, Stony Creek district, Carter Co., northeastern TN. Occurs in Erwin formation of Iron and Holston Mountains. There it consists of so-called "transition beds" of earlier reports. A section of the member at Helenmode mine was described by Stose and Schrader (1923) as consisting of about 100 ft of yellow, finely laminated clays (which were once calcareous shales) and some mealy arkosic sandstones, some of which are stained red or purple from iron, others green from glauconite grains. Coarse grits of rounded quartz grains are found at the top. Overlies upper quartzite member of Erwin; underlies Shady dolomite. Helenmode on Embreeville Mountain in Bald Mountain thrust sheet is a thin bed of shale with local upper bed of coarse sandstone. In southwest part of Mountain City window, occurs as poorly exposed shaly beds, about 50 ft thick. Coarse-grained sandstone containing SCOLITHUS [SKOLITHOS] occurs at its top in Butler district. Age is Early Cambrian.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode member
- Modifications:
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- Areal extent
- AAPG geologic province:
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- Appalachian basin
- Piedmont-Blue Ridge province
Summary:
Extended into Madison Co., western NC as a member of Erwin formation.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode member*
- Modifications:
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- Revised
- AAPG geologic province:
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- Appalachian basin
Summary:
Shown as member at top of both Hesse sandstone and Erwin formation.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode formation*
- Modifications:
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- Revised
- Biostratigraphic dating
- AAPG geologic province:
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- Appalachian basin
Summary:
Rank raised to Helenmode formation of Chilhowee group. Contains OLENELLUS at Little River Gap in Chilhowee Mountain, TN; because of this occurrence, Helenmode is classed as Cambrian and the rest of Chilhowee group below it is Precambrian(?).
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode member*
- Modifications:
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- Revised
- AAPG geologic province:
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- Appalachian basin
Summary:
In northeasternmost TN considered uppermost member of Erwin formation. Overlies Hesse quartzite member; underlies Shady dolomite. Unit mapped around whole periphery of Shady Valley and Stony Creek Valley where it has thickness of 100 ft or a little less; 67 ft thick in section on US Hwy 19E south of Valley Forge. Coarse sandstone bed here placed at top of Helenmode has been variously classified by others; in southwestern VA, a similar layer has been called initial deposit of Shady dolomite. Age is Early Cambrian.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode formation*
- Modifications:
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- Overview
- AAPG geologic province:
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- Appalachian basin
Summary:
Helenmode formation overlies Hesse quartzite; underlies Shady dolomite. Most of Chilhowee group is questionably assigned an Early Cambrian age because recoverable fossils of Early Cambrian age are confined to Helenmode, youngest formation of Chilhowee.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Helenmode Member
- Modifications:
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- Overview
- AAPG geologic province:
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- Appalachian basin
Summary:
Used as Helenmode Member of Hesse Sandstone of Cambrian age.
Source: GNU records (USGS DDS-6; Reston GNULEX).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).