Glaciomarine deposits of Miocene through Holocene age in the Yakataga Formation along the Gulf of Alaska margin, Alaska
By: George Plafker and W. O. Addicott
Edited by: Thomas P. Miller
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Abstract
Perhaps the world's longest and most complete onshore sedimentary record of late Cenozoic glaciation is preserved in the Gulf of Alaska Tertiary province that extends 800 km along the coast of southern Alaska. The Yakataga Formation, with an aggregate outcrop thickness of about 5,000 m, is characterized by variable amounts of distinctive neritic marine tillite-like diamictite and laminated siltstone containing dropstones interpreted as ice-rafted glacial debris. The lithology, sedimentary structures and molluscan fauna of the formation suggest that active tidal glaciers or an ice shelf were present along the landward margin of the basin possibly beginning in early or early middle Miocene time. Dropstone distribution in outcrop sections indicates that glaciers reached tidewater intermittently during the Miocene and were almost continually present throughout the Pliocene and much of the Pleistocene. Paleomagnetic and nannoplankton dating of the upper 1,181 m of the Yakataga Formation at Middleton Island indicate that this part of the sequence probably was entirely deposited during the Matuyama reversed polarity epoch of the Pleistocene during which the sedimentation rate was of the order of 1 m/1,000 years. Lithologically similar deposits of poorly consolidated sandy mud and pebbly mud continue to accumulate locally near tidal glaciers in the same area, and older late Quaternary deposits are undoubtedly present offshore. The anomalous late Cenozoic glaciation recorded in the sediments along the Gulf of Alaska margin reflects a fortuitous combination of a subsiding shelf basin adjacent to an area of extremely high elevations and exceptionally heavy precipitation, an environment that persists to the present.
Study Area
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Glaciomarine deposits of Miocene through Holocene age in the Yakataga Formation along the Gulf of Alaska margin, Alaska |
| Year Published | 1976 |
| Language | English |
| Publisher | Alaska Geological Society |
| Publisher location | Anchorage, AK |
| Description | 23 p. |
| Larger Work Type | Book |
| Larger Work Subtype | Conference publication |
| Larger Work Title | Recent and ancient sedimentary environments in Alaska: Proceedings of the Alaska Geological Society Symposium held April 2-4, 1975, at Anchorage, Alaska |
| First page | Q1 |
| Last page | Q23 |
| Country | United States |
| State | Alaska |
| Google Analytic Metrics | Metrics page |