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Map showing publication footprint
  • Usage in publication:
    • Cynthia Falls member
  • Modifications:
    • First used
  • Dominant lithology:
    • Sandstone
  • AAPG geologic province:
    • Alaska Southwestern region
Publication:

Kellum, L.B., 1945, Jurassic stratigraphy of Alaska and petroleum exploration in northwest America: New York Academy of Sciences Transactions, 2nd series, v. 7, no. 8, p. 201-209.


Summary:

Listed in stratigraphic table as underlying and overlying unnamed sandy shale members of Tuxedni formation. Composed of medium-grained gray sandstone grading horizontally into alternating sandstone and conglomerate. Is 800 ft thick. Age given as Middle Jurassic based on fossils.

Source: GNU records (USGS DDS-6; Menlo GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Cynthia Falls sandstone member*
  • Modifications:
    • Named
  • Dominant lithology:
    • Sandstone
    • Siltstone
  • AAPG geologic province:
    • Alaska Southwestern region
Publication:

Kirschner, C.E., and Minard, D.L., 1948, Geology of the Iniskin Peninsula, Alaska: U.S. Geological Survey Oil and Gas Investigations Map, OM-95, 1 sheet, scale 1:4,800


Summary:

Named as lowermost named member (of 3) of Tuxedni formation for conspicuous waterfall on Hardy Creek, Iniskin Peninsula, southwestern AK. Forms hogback ridges along flanks of Tonnie syncline and Fitz Creek anticline. Well exposed in nearly all creeks tributary to Fitz Creek from the west. Consists of thick-bedded to massive, medium- to coarse-grained sandstone that is dark gray green, weathering to light gray. Contains bed of arenaceous siltstone near middle part. Is 600 to 900 ft thick. Overlies unnamed siltstone member; underlies Bowser member (new) (both of Tuxedni formation). Contains few fossils. Age given as Middle Jurassic in correlation chart.

Source: GNU records (USGS DDS-6; Menlo GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Cynthia Falls Sandstone*
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Alaska Southwestern region
Publication:

Detterman, R.L., 1963, Revised stratigraphic nomenclature and age of the Tuxedni Group in the Cook Inlet region, Alaska, IN Geological Survey Research 1963: U.S. Geological Survey Professional Paper, 475-C, p. C30-C34.


Summary:

Cynthia Falls Sandstone Member (of Tuxedni Formation) of Kellum (1945) is raised in rank to 4th from lowermost formation (of 6) of Tuxedni Group. Type section is designated on Tonnie Creek, starting 5600 ft S 50 deg E of Tonnie Peak, continuing upstream for 600 ft, Iniskin Peninsula, southwestern AK. Conformably overlies Fitz Creek Siltstone (new); conformably underlies Twist Creek Siltstone (new) (both of Tuxedni Group). Age given as Middle Jurassic (Bajocian).

Source: GNU records (USGS DDS-6; Menlo GNULEX).


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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 ([ ]).

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