KENAI FJORDS NATIONAL PARK

by Kelsey Garner, 2004

A glacier within the park.from http://www.nps.gov.

Background

Kenai Fjords National Park was proclaimed a national monument on December 1, 1978 and established as a national park December 2, 1980 in Seward, Alaska on the Kenai Peninsula. The Harding Ice sheet (the largest ice sheet within the United States), 38 other glacial systems, and onshore and offshore wildlife (Orcas, otters, puffins, bear, moose and mountain goats) were reason to create this park. Kenai Fjords is only 80 miles from Anchorage, Alaska, but the park is still very isolated and hard to travel to (Harris and Tuttle). The park’s area is 669,983 acres, and approximately 1,047 square miles of mainly untouched land. The park receives around 250,000 vistors per year (nps.gov).

 

Harding Ice Sheet from: http://community.webshots.com/album/89701015CLzzgD.

The Kenai Fjords are lithologically and structurally part of the Kenai-Chugach Mountains. The range extends eastward along the Kenai Peninsula along the Gulf of Alaska. At the bottom of the ocean, there is evidence of glaciers because of the 300-foot deep contour that is associated with glacial deposits left during an advance of the glacier before the Holocene sea level rise. At one time, the glaciers were over 3000 feet thick in many of the valleys. Very few places were unaffected by the glacial events. The last major glacial event in Alaska was 14,000-10,000 years ago (Harris and Tuttle).
The weather has warmed very little since the ice age and there is still 200 inches of precipitation per year including 500-1000 inches of snow before it is compacted. “Two to four times as much precipitation falls as snow…than as rain…” (Harris and Tuttle). The temperature ranges from 40-60 degrees in the summer and there still can be freezing weather during those months.

Exit Glacier from: http://community.webshots.com/album/89701015CLzzgD.

Geologic Background (based on Harris and Tuttle, 1990)

Many gaps exist in the rock record at Kenai Fjords, partially because there are few outcrops because of the ice sheets. The oldest rocks are from the Triassic to Cretaceous, which are named the McHugh Complex. That rock unit is composed of a mélange of siltstone, sandstone, conglomerate, tuff, pillow basalt, chert, limestone, and argillite. On top of the McHugh Complex is the Valdez Group, which is the most predominant rock group in the park, which is from the Upper Cretaceous. It is composed of dark colored metasedimentary flysch, sandstone, siltstone, and conglomerate. There are no fossils within this group, so it was hard to date this series (Lexicon). Both the McHugh Complex and the Valdez Group are part of the belt of rocks that extend the coast of the Gulf of Alaska all the way to the Shumagin Island in the Aleutians. Next in the sequence is the Orca group from the Eocene. This rock unit consists of dark gray flysch rocks and turbidites. There is not apparent break between the Valdez and Orca groups. Scientists think that they originated from a similar source. In addition, within the Eocene epoch, granitic batholiths, small plutons and dikes were formed. The granite outcrops from the batholiths underneath Harding Icefield are seen in glacial troughs and cirques on the side of the mountains. Following the Orca Group is Granitic Intrusions in the Oligocene. There is a major gap between the Eocene and the Pliocene. Once you reach the Quaternary all you find is alluvium and glacial drift. All of the rock units are in my stratigraphic column in MS Word or PDF format and part o

f the Geologic Map (by Bradley and Donley) of Kenai Fjords.


UPDATE: Here is the new column in MS Word. Here is the new map of the area in PDF format. Here is a PowerPoint poster that was presented at the GSA meeting in November 2004.

References:

http://www.nps.gov/kefj/index.htm
Bradley, Dwight and Tom Donley. May 1995. Geological Map of Kenai Fjords National Park and Vicinity. U.S. Geological Survey
Bradley, D.C, Kusky, T.M., Haeussler, P.J., Karl, S.M., and Dudley, D.T.;1999; Geologic Map of the Seldovia Quadrangle, South-Central Alaska: USGS Open File report OF 99-18, http://geopubs.wr.usgs.gov/open-file/of99-18/
Harris, Ann G., and Tuttle, Esther. 1990. Geology of National Parks. 4th ed., Kendall/Hunt Publishing Co..
Lexicon of Geologic Names of the United States for 1968-1975, Geologic Survey Bulletin, 1520
Tysdal, R.G., and J.E. Case. Geologic Map of the Seward and Blying Sound Quadrangles, Alaska. U.S. Geol. Surv. Misc. Invest. Series Map I-1150, 1979, 12 pp.

11/2004