- Usage in publication:
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- Kelp Bay Group*
- Modifications:
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- Named
- Dominant lithology:
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- Schist
- Graywacke
- Conglomerate
- Slate
- Phyllite
- AAPG geologic province:
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- Alaska Southeastern region
Summary:
Type area designated as exposures along shores of Kelp Bay, northern Baranof Island, southeastern AK. Forms parts of Krestof Island and most of northeast half of Partofshikof Island. Composed of fissile quartzose greenschist and phyllite; graywacke, slate, and sheared conglomerate; calcareous and quartzose slate that contains lenses of metachert and volcanic rock; and granular-appearing, moderately platy siliceous greenschist that contains lenses of jasper. Jasper-bearing beds are separately mapped on geologic map of northern Baranof Island. At head of Nakwasina Sound contact with underlying Nakwasina Group (new) is covered; units seem to be structurally discordant. Disconformably underlies Sitka Group (new). Provisionally assigned to Triassic(?) age on basis of meager fossil evidence and comparison to similar rocks.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Kelp Bay Group*
- Modifications:
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- Areal extent
- Age modified
- Biostratigraphic dating
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
Unit geographically extended to southwestern Chichagof Island. Scleractinian coral (Helen Duncan, written commun., 1961) found in limestone of unit on northeast shore of Slocum Arm is Triassic or Jurassic in age. On this basis Kelp Bay Group is considered to be Triassic or Jurassic age.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
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- Kelp Bay Group*
- Modifications:
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- Revised
- Age modified
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
Kelp Bay Group is redefined to include (ascending): Goon Dip Greenstone, Whitestripe Marble, Pinnacle Peak Phyllite, Waterfall Greenstone, Khaz Formation (new), schist unit of Reed and Coats (1941) on western Chichagof Island. Group includes Khaz Formation and 3 unnamed units on Baranof Island. In parts of Baranof Island, group is not subdivided. Kelp Bay Group of Loney and others (1963) is renamed Khaz Formation. Katlian Group of Loney and others (1963) is abandoned ; its rocks now included in Kelp Bay Group. Group also includes rocks of now abandoned Nakwasina Group. Age is considered to be Triassic and (or) Jurassic on basis of scanty fossil evidence.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Kelp Bay Group*
- Modifications:
-
- Revised
- Areal extent
- Age modified
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
Kelp Bay Group is complicated, heterogeneous assemblage of fault-bounded metavolcanic and metasedimentary rocks on northern Baranof, western Chichagof and Yakobi Islands. Group is restricted to Chugach terrane, thus restricting group to: Khaz Formation and Freeburn assemblage which includes Waterfall Greenstone and Pinnacle Peak Phyllite. Goon Dip Greenstone and Whitestripe Marble are removed from group as they are included in Wrangellia terrane which is separated from Chugach terrane by Border Range fault. Age of Kelp Bay Group is Cretaceous and Cretaceous(?).
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Kelp Bay Group*
- Modifications:
-
- Age modified
- Biostratigraphic dating
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
Megafossils (BUCHIA FISCHERIANA) collected on Baranof Island from Khaz Formation of Kelp Bay Group indicate Late Jurassic age for part of group. [Age of group thus is Late Jurassic and Cretaceous and Cretaceous(?).]
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Kelp Bay Group*
- Modifications:
-
- Age modified
- Biostratigraphic dating
- Geochronologic dating
- AAPG geologic province:
-
- Alaska Southeastern region
Summary:
(advance copy). Age of group is Late Jurassic to mid-Cretaceous [depositional age] based on fossil ages (Early Cretaceous) and radiometric ages (106 to 91 Ma).
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 ([ ]).