- Usage in publication:
-
- Irish Gulch Slate*
- Modifications:
-
- Named
- Reference
- Dominant lithology:
-
- Slate
- AAPG geologic province:
-
- Midcontinent region
Summary:
Named for exposures on west side Irish Gulch, sec 14, T2N, R3E, its type locality, Lawrence Co, SD, in the Midcontinent region. Reference locality designated along Greens Gulch in sec 2, T2N, R3E. Composed of gray to black sericitic to sparkling micaceous slate without obvious laminae or color banding. Near base a single thin chert-grunerite unit persists along strike for several mi. Very generalized description of lithology. Areal extent beyond report boundaries not discussed. Overlies Moonshine Gulch Quartzite (new). Underlies Montana Mine Formation (new) of Flag Rock Group (rank raised). Thickness not stated. Exposed in central and western part of Rochford anticlinorium, and thins to northwest and to southeast. Tentatively correlated with Northwestern Formation. Of middle Precambrian age. Geologic map.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Irish Gulch Slate*
- Modifications:
-
- Age modified
- AAPG geologic province:
-
- Midcontinent region
Summary:
Mapped with Early Proterozoic unit Xsi (pl. 1) in Rochford area, Pennington Co, SD in Midcontinent region. Is correlated with the Northwestern Formation of the Lead area, Lawrence Co. Geologic map.
Source: GNU records (USGS DDS-6; Denver 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 ([ ]).