- Usage in publication:
-
- Nizina Mountain Formation*
- Modifications:
-
- Named
- Biostratigraphic dating
- Dominant lithology:
-
- Graywacke
- AAPG geologic province:
-
- Alaska Southern region
Summary:
Named for type locality, outcrops that partly girdle ridge that extends southward from Nizina Mountain, McCarthy C-5 quad, southern AK. Except for isolated outcrop in McCarthy C-6 quad, unit is recognized only in McCarthy C-5 quad. Consists of fine-grained to very fine-grained graywacke associated with shaly partings and few limy lenses and concretions. Is mainly dark greenish gray weathering to reddish brown. Thickness is about 1350 ft at type locality. Disconformably overlies Lubbe Creek Formation (new) and locally McCarthy Formation. Disconformably underlies Root Glacier Formation (new) and locally Cretaceous sedimentary rocks, Wrangell Lava or Quaternary surficial deposits. Age is Middle and Late Jurassic based on fossils identified by R.W. Imlay (written commun.,1963).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Nizina Mountain Formation*
- Modifications:
-
- Age modified
- AAPG geologic province:
-
- Alaska Southern region
Summary:
Correlation chart shows age is Middle Jurassic (Bajocian to Bathonian) based on paleontological evidence.
Source: GNU records (USGS DDS-6; Menlo 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 ([ ]).