- Usage in publication:
-
- Freshwater Bay formation*
- Modifications:
-
- Named
- Biostratigraphic dating
- Dominant lithology:
-
- Greenstone
- Rhyolite
- Andesite
- Limestone
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
Type locality designated near head of Freshwater Bay, Chichagof Island, southeastern AK. Forms northwestward-trending belt of exposures averaging 2 mi wide at Freshwater Bay on southwest limb of Freshwater syncline. Belt widens to more than 3 mi to northwest near margin of map of Freshwater Bay area. Is thick sequence of volcanic and intercalated sedimentary rocks. Divided into (ascending): lower greenstone member, middle rhyolitic member, and upper andesitic member on southwest limb of syncline. Measured section on northeast syncline is over 4450 ft thick. Thickness is estimated to range from 4500 to about 6500 ft. Unconformably overlies Cedar Cove formation (new) of Middle and Late(?) Devonian age and in places Kennel Creek limestone (new). Disconformably underlies Iyoukeen formation (new) of Mississippian age. Age is Late Devonian (Frasnian) based on fossils in limestone at Port Frederick considered to be part of unit.
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 ([ ]).