Tectonic controls on marine terrace origin and character in the Lituya Bay area, eastern Gulf of Alaska
Description
Tectonic controls on marine terrace origin and character in the Lituya Bay area, eastern Gulf of Alaska, Report of Investigation 2022-4, presents radiocarbon data collected from deformed terraces along 65 km of the coast between Fairweather Glacier and Icy Point in the Lituya Bay area of the eastern Gulf of Alaska. From Fairweather Glacier to Lituya Bay one prominent terrace flanks the coastal mountain front, and isolated remnants of a lower, younger terrace occur landward of a wide prograded coastal plain. From Lituya Bay to Crillon River a sequence of five well-developed terraces bevel the coastal foothills. From Finger Glacier to Icy Point four terraces and the possible remnants of a fifth occur. The terraces form an arch with an axis of maximum uplift near La Perouse Glacier. The deformation is progressively greater in the older terraces and shoreline angle relief on the highest terrace is 100 m or more. The terraces are of Pleistocene and Holocene age. The oldest terrace studied is not well dated but the next oldest may have formed during the post-Wisconsin sea level rise. The three Holocene terraces probably formed about 3,500 (3,990-2,960 cal yr BP), 1,000, and 500 years ago. Ongoing uplift and arching of the coastal zone may mark renewal of mid-Pleistocene folding, but Holocene uplift has taken place as discrete events that were probably accompanied by earthquakes. At least five uplift events have taken place between Lituya Bay and Icy Point in the past 3,000 to 4,000 years, which imply an average recurrence interval of ~500 years. Because recurrence of events that uplifted the terraces is distinctly longer than the average earthquake recurrence interval for the nearby Fairweather fault, coastal uplift may occur independently. The Finger Glacier fault displaces the Holocene terraces and may be a developing link between the onshore and offshore segments of the Fairweather fault. Sample descriptions, locations, and types are included in the analytical data table. The data are available from the DGGS website: http://doi.org/10.14509/30903.
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https://doi.org/10.14509/30903 |
Tags
- coastal and river
- pleistocene
- tectonics
- marine geology
- topsy formation
- debris flow deposit
- terrace
- faults
- earthquake related slope failure
- holocene
- tertiary
- uplift
- dggs
- cenotaph volcanics
- coastal
- gulf of alaska
- yakataga formation
- marine
- faulting
- earthquake
- finger glacier
- fault displacement
- eagle creek
- portage creek
- deepwater depositional system
- lituya bay
- miocene
- tsunami
- fairweather glacier
- cape yakataga
- coastal plain
- debris flow