Date of Award


Document Type


Degree Name

Master of Science (MS)


Ocean & Earth Sciences



Committee Director

Randall Spencer

Committee Member

Thomas M. Cronin

Committee Member

Stephen J. Culver

Committee Member

Dennis A. Darby

Call Number for Print

Special Collections LD4331.G4L64


This study records and analyzes ostracode assemblages recovered from sediments assigned to the Late Pliocene Tuapaktushak and Middle Pleistocene Karmuk members of the Gubik Formation in the Skull Cliff area of the Arctic Coastal Plain in western Alaska. Forty-three species were identified from 47 samples (25 from the Tuapaktushak Member and 23 from the Karmuk Member). Samples were grouped by Q-mode cluster analysis and by member assignment for the purpose of analysis.

Paleoenvironmental analyses of ostracode assemblages representative of each cluster suggest all samples, regardless of cluster membership, were deposited in similar marine environments where water depths were in the inner to middle neritic range, salinities were normal with local variability, and the marine climates were frigid to subfrigid. Paleoenvironmental analyses of ostracode assemblages by member assignment suggest the Tuapaktushak and Karmuk Members were both deposited in environments similar to those described above and the environments during deposition of each member were not significantly different, even though the two members were deposited during two different eustatic high sea level events separated by at least 1.64 million years.

The fact that all of the extant marine ostracodes, except Pectocythere marinkovichi, identified to the species level from samples assigned to both members, are recognized constituents of modern, shallow water, Arctic assemblages indicates modern Arctic assemblages were present by the time the Tuapaktushak Member was deposited which was 2.48 to 2.41 Ma.

The comparison of the Skull Cliff ostracode fauna to other contemporaneous high latitude faunas revealed a number of similarities and differences with the most similar faunas being the Fish Creek and Colvillian and Bigbendian faunas from the North Slope area of Alaska. Even though Skull Cliff, Alaska and Tjornes, Iceland are not in close proximity, the paleoclimatic interpretation made with regards to the deposition of the Tuapaktushak fauna fit into and confirm the cooling trend suggested for the Tjornes area of the Arctic between 3.0 and 1.5 Ma.


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