Jeannette
M Yarnell
Paleontology of two North American Triassic reef faunas: implications
for terrane paleogeography
Director: George Stanley
Massive Upper Triassic (Norian) reef limestone at Lime Peak Yukon and smaller deposits of reef associated carbonates at Long Creek, Alaska contain a variety of shallow-water marine fossils that are significant for paleobiogeographic reconstruction of terranes. Eleven scleractinian coral species and the alatoform bivalve, Wallowaconcha cf. W. raylenea are described critically for the first time from the Stikine terrane at Lime Peak, Yukon. In addition, the new discovery of five scleractinian coral species, the alatoform bivalve Wallowaconcha sp and one spongiomorph is also reported from the Chulitna terrane at Long Creek Alaska.
The newly described coral species from the Stikine and
Chulitna terranes were added to a database comprised of 57 Triassic
scleractinian coral species from seven North American displaced terranes,
and one Siberian terrane The database was subjected to probabilistic
similarity, cluster, and parsimony analysis in order to reconstruct
terrane paleogeography based on faunal similarity. Results from the
statistical analyses were compared with known paleomagnetic, stratigraphic,
and tectonic data, as well as other paleogeographic interpretations
to create a paleobiogeographic terrane reconstruction for the Triassic.
Observations of the occurrence of wallowaconchid bivalves in both the
Stikine and Chulitna terranes also were incorporated into the terrane
reconstruction.
Results from the probabilistic similarity, cluster, and parsimony analyses
are generally conformable and show temporal and spatial relationships
within two main groups: 1) the Stikine, Chulitna, Quesnel, Eastern Klamath
Luning Allochthon, and Antimonio terranes, and 2) the Wrangellia, Alexander
Wallowa and Koryak terranes. These groups are interpreted to represent
at least two ancient island arc chains that developed along the western
margin of North America during Triassic time.
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