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Reference
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| Title: |
Ordovician, Silurian, and Devonian corals of Alaska
,
1975
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Abstract Corals are common in Ordovician, Silurian, and Devonian rocks from Alaska, but few have been described or illustrated. Most of the known occurrences of corals are in carbonate rocks, either in an east-west belt of shelf facies across central Alaska that presisted from pre-Ordovician to Middle Devonian time or in a more southerly volcanic graywacke belt of geosynclinal facies that includes significant limestone units in southeastern Alaska. Corals occur in other areas but are less well known.
Annotated lists of corals summarize most collections made by U.S. Geological Survey geologists in the last 15 years. Many of the corals are illustrated. |
| Report by: |
William A. Oliver
, Jr.
,
C. W. Merriam
,
Michael Churkin
, Jr.
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| | Age: | Middle Ordovician-Late Ordovician (late Middle Ordovician - early Late Ordovician) |
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| Comment: | A lower assemblage (table 1) contains only Labyrinthites) (Labyrinthites) sp. (identified, discussed and illustrated by Bolton, 1965, p. 21-22, pl. 7, fig. 4) and Reuschia sp. Bolton considered the Labyrinthites to be of Middle Ordovician age but did not discuss this assignment. Sainsbury (1969a, p. 30-31; in Sainsbury and others, 1971, p. 56) considered the field evidence to indicate a Middle Ordovician age, but the fossils on which this determination was based were not associated with the corals. Labyrinthites occurs in both Middle and Upper Ordovician rocks (Bolton, 1965, p. 23); Reuschia is uncommon but previously known only from the Upper Ordovician (and Lower Silurian(?)). I conclude that the assemblage is late Middle to early Late Ordovician in age but almost certainly older than the Late Ordovician assemblage discussed in the next paragraph. (from Oliver et al., 1975, p. 23) |
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