- Usage in publication:
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- Yadkin Graywacke
- Modifications:
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- Named
- Dominant lithology:
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- Graywacke
- Sandstone
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Yadkin Graywacke named in Stanly Co., central NC, and assigned to top of Albemarle Group. Consists of dark-green graywacke sandstone containing interbeds of mafic tuffaceous argillite, mafic lithic-crystal tuff, and felsic lithic tuff. Occurs only west of Troy anticlinorium. Crops out along axis of a southwest plunging fold (New London syncline), which is west of the anticlinorium. Crops out in area about 5 mi wide and has been traced along axis of syncline from New London southward to west of Monroe, a distance of 35 mi. Unit is only thick sequence of graywacke in Carolina slate belt. Thickness at least 3,000 ft. Conformably overlies McManus Formation (new) of Albemarle Group; unconformably overlain by mafic pyroclastics of Tater Top Group (new). Age is early Paleozoic.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Member*
- Modifications:
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- Revised
- Age modified
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Yadkin Graywacke reduced to member rank and assigned to Millingport Formation. Age of Yadkin changed from early Paleozoic to Ordovician(?).
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Member*
- Modifications:
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- Age modified
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Age of the Millingport Formation changed from Ordovician(?) to Cambrian.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Formation*
- Modifications:
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- Revised
- Age modified
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Millingport Formation abandoned and its Floyd Church and Yadkin Members raised to formation status within the Albemarle Group. Age of the Albemarle and its four formations (Tillery, Cid, Floyd Church and Yadkin) changed to latest Proterozoic on the basis of the fossil PTERIDINIUM, diagnostic of Vendian-Ediacaran fauna, identified from the middle or upper Floyd Church Formation. This had previously been misidentified as a Cambrian trilobite. A U/Pb concordia-intercept date of 586+/-10 Ma for zircons in the upper Uwharrie Formation sets a maximum age limit for the Albemarle.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Formation
- Modifications:
-
- Overview
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Yadkin Formation assigned a Late Proterozoic to Cambrian age on the State map. Albemarle Group not used.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Graywacke
- Modifications:
-
- Overview
- Revised
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Authors adopt the terminology established by Conley and Bain (1965) as modified by Gibson and Teeter (1984: Carolina Geol. Soc. Field Trip Guidebook). Yadkin Graywacke of Albemarle Group overlies McManus Formation (reinstated) in this report. Age not stated.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Yadkin Formation*
- Modifications:
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- Geochronologic dating
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Rb-Sr whole-rock isochron age of 540 +/-7 Ma (Black, 1978; recalculated by Milton, 1984; Harris and Glover, 1988) was obtained from a mafic volcanic lentil in Yadkin Formation at top of Albemarle Group, suggesting that Yadkin is Cambrian.
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 ([ ]).