Tag Archives: Chichagof Island

When an Island was an Ocean

Fossils on a Mountaintop

It is so easy to forget that the world as you know it is a tiny snapshot in time. It is has been changing for millions of years by raising mountains and wearing them back to dust and by carving out oceans and filling them in again. Many time, if you look closely, the places we know are filled with clues of a different time. You don’t expect to find fossils on a mountain top, but on Chichagof Island small, shelled creatures are frozen in rock among the lichens and deer trails. Their presence are a time capsule of life 360-375 million years ago just waiting to be discovered!

Chichagof Island, Fossil, Devonian
This unique fossil was found in a rock quarry outside of Hoonah, Alaska on Chichagof Island.

Hoonah, Alaska has an extensive road network – 300 miles of road wind through forests of Spruce and Hemlock. Making a road takes a lot of rock and that has resulted in dozens of rock pits scattered throughout the road system. I had heard of fossils on the mountaintops, but a discovery by a coworker a few years ago of fossils in a rockpit made them more attainable to see and document. I recently drove the miles of winding roads to that pit with a camera in hand to learn-about-and-observe life long ago.

Chichagof Island, Fossil, Devonian
A small fossil perfectly preserved in a rock face. As you can see – it isn’t big!

Like cracking an egg the pieces of rock were jigsaw puzzle pieces that contained clues of the lives of Devonian creatures. In the pit, we found a variety of forms of animals frozen in the rock and some of them reminded me of animals in the oceans today. Shells, sponges, corals, and some trilobites! Seeing them caused me to reflect on “deep time” and the evolution of species – it also reminded me of how little I knew about the geologic history of the island of geology itself! What were the names of these creatures? What type of rock were they buried in? Why had they been lifted up from the ocean bottom to this spot?

Geology Research

I began to research the geologic history of Chichagof Island and discovered the region is well researched. For decades the USGS, Forest Service, and other research institutions had documented the bedrock and formations of Chichagof. Through a USGS Map viewer I learned that much of northern Chichagof Island was classified as the “Freshwater bay” formation. I read through the description of the formation on the website and couldn’t help but think of one thing : look at all that jargon! Scientific jargon is almost impossible to comprehend unless you are in the field, so I made it my mission to crack the jargon.

I copied the description below from the USGS website to describe the Freshwater Formation. Once you’ve read through it skip to the next section to crack the jargon!

“Freshwater Bay Formation on Chichagof Island is composed of green and red andesite and basalt flows, breccia, and tuff, pyroclastic rhyolite deposits, minor amounts of interbedded conglomeratic volcanic graywacke, grayish-black argillite, and dark-gray limestone (Loney and others, 1963). The correlative but more sedimentary-rock-rich Port Refugio Formation on Prince of Wales Island consists of km-thick sections of siltstone, shale, volcanogenic graywacke, conglomerate, and minor limestone that alternate with km-thick sections of pillow basalt intercalated with minor chert, shale, limestone and aquagene tuff (Eberlein and others, 1983). Unit also includes the Coronados Volcanics and the Saint Joseph Island Volcanics found on western Prince of Wales Island and adjacent islands (Eberlein and others, 1983). The Port Refugio Formation may be a distal facies of the Freshwater Bay Formation. Eberlein and Churkin (1970, p. 43) stated that “many of the graywackes are largely reworked basaltic lavas that contain euhedral crystals of plagioclase and pyroxene that resemble the phenocrysts in the basaltic flows of the formation,” and that many of the conglomerate clasts are andesitic or basaltic rocks. Volcanic flows are found throughout the unit and are up to a hundred meters thick (Eberlein and Churkin, 1970). Age control from the Freshwater Bay is derived from included brachiopods, including Cyrtospirifer, mollusks, and corals of Frasnian (Late Devonian) age (Loney and others, 1975) and conodonts of Famennian (Late Devonian) age (Karl, 1999). Eberlein and Churkin (1970) reported Late Devonian “beautifully preserved” brachiopods that Savage and others (1978) assigned a middle to late Famennian age and that are associated with vascular plant fossils”

Alaska USGS https://alaska.usgs.gov/science/geology/state_map/interactive_map/AKgeologic_map.html

Breaking Down the Rock Jargon

Not sure about rocks of the Devonian Era? Come learn along with me!

Breaking Down the Animal Jargon

As if life these days isn’t hard to enough to keep track of check out all the names of the creatures that lived long ago!

  • brachiopods,
  • Cyrtospirifer,
  • mollusks,
  • and corals of Frasnian (Late Devonian) age (Loney and others, 1975) and conodonts of Famennian (Late Devonian) age (Karl, 1999). Eberlein and Churkin (1970) reported Late Devonian “beautifully preserved” brachiopods that Savage and others (1978) assigned a middle to late Famennian age and that are associated with vascular plant fossils
    • Deep time is a crazy, crazy thing. The chart above does an adequate job of showing off the “Devonian Era” in purple. It’s far before the time of the dinosaurs. Humans have been around for about 200,000 years and the T-Rex lived during the Cretacous Period. Life was really just getting going in the Devonian period!

I know this will not be the last time that I come across fossils on Chichagof Island. I look forward to when I do and to expanding my knowledge of a time long past.

The Pine Marten Transplants of Chichagof Island

When I think of the American Pine Marten (Martes americana), it invokes an image of giant, rotund spruces and hemlocks in an old growth forest. In my mind, the lithe body of a Pine Marten scurries around in the branches perhaps a hundred feet from the forest floor in search of a red squirrel or bird’s nest. A small squeak indicates that the small mustelid has connected with its prey. This vision could be considered “classic” in the fact that martens are strongly associated with mature, old growth forests (Greg 1995). In fact, their dependence on old growth forests is so strong that traditional logging methods have been cited as a driver of large scale declines of marten populations (Davies 1983). In some regions of Southeast Alaska marten are still abundant, and in general the Tongass National Forest offers great habitat for marten. However, they are most often found on the mainland, and I was told by a friend that they were introduced to Chichagof Island by people. That tidbit of information intrigued me, and as I dove into Pine Marten history on Chichagof I was very interested to find out a marten I crossed paths with is a descendant from a small introduction of intentional transplants.


Transplanting wildlife to new areas in Alaska has been going on since the Russians began to settle  here (Paul 2009). Frequently transplants happened on the Aleutian Islands or the islands of Southeast Alaska and often the incentive revolved around economic opportunity. A well-known example of this is the transplant of Blue Fox to the Aleutians so they could be farmed and harvested for trapping.  The fox were responsible for extirpating several species of birds from the islands.  Over the years many species including Caribou, Sitka Blacktail, Mountain Goats and Elk have been introduced to new areas throughout Alaska. The first martens were introduced to Chichagof Island in 1949 to create a population for trapping (in fact Pine Martens are still Alaska’s largest fur market earning 1-2 million annually (Alaska Department of Fish and Game)). By 1954, 21 marten had been introduced to the Island and despite the low number of starting individuals, their numbers climbed rapidly in their new environment. It is estimated in 2006 over 2,200 marten were trapped on Chichagof Island. It’s a remarkably successful population here!

Blue Fox
It was fascinating to see this account from the early 1900s of Blue Fox farming. At the time it was implemented as a branch of the USDA. You can read the full text at : https://archive.org/details/bluefoxfarmingin1350ashb

Since transplants can have negative effects on resident populations, did the transplant of marten to Chichagof Island impact populations there? Anecdotally I have been told that Dusky Grouse (Dendragapus obscurus) numbers have declined on the island and that Northern Flying Squirrel (Glaucomys sabrinus) are not as abundant as they used to be.  Certainly each of these prey items are consumed by the martens. Buskirk (1983) found birds and squirrels made up a strong majority of the marten’s diet in Southcentral Alaska, but that voles, mice, and shrews were the most important items in the diet.  On Chichagof Island, the diet patterns are the same, although Ben-David et al. (1997) found high variation in the autumn and the presence of salmon and crab.  In the summer a marten’s diet may be made up 80% of birds and squirrels. Marten populations are normally not very large and hence would be unlikely to strongly influence prey, but Chichagof Island holds the highest abundance in the region (Flynn and Ben-David 2004). With these high populations and a diet favoring birds and squirrels, is it is possible that marten populations on Chichagof Island exert a top-down pressure on their prey? I believe based on the effect of being a successful transplant makes it it possible. However, I can find no data on the population trends of Dusky Grouse or Flying Squirrels on Chichagof Island and there are many other factors at play. For instance,  Dusky Grouse may find protection from predators in old growth  and flying squirrels are likely to benefit from old growth structure. Hence, removal of old growth by logging may lead to a reduced population. Rather than conjecture on a speculative answer, I will put it out there that a graduate student and the Alaska Department of Fish and Game could pair up on this venture.

I will leave you with a description of my encounter with an American Pine Marten. On October 16th, Hoonah received measurable snow before Fairbanks, Alaska.  The 14 inches of snow that lay on the ground was the first time Southeast Alaska had beat the Interior to snow in over 70 years. I started up my truck, my wife jumped in, and we headed out the road with the hope of photographing a bear in the snow. The lower elevations were slick and wet. 6 inches of slush lay heavy on the roads, but we made it the 10 miles to the turn towards False Bay. As we slowly climbed the pass the truck seemed to shrink into the ground as the snow levels rose. After only a couple of miles we were plowing snow with the bumper of the truck and it was evident that we would not go much further. The only catch was we could not find a place to turn around. On we drove hoping that our luck held out, when up the road we saw a small figure bound into the ditch. It plowed into a snow drift and then burst back out again. In a flash I was out with my camera clicking away. Pursing my lips I made small rodent sounds which intrigued the inquisitive creature. Turning its head rapidly it dove back into a snow bank and emerged a few feet away. To me it seemed as if the little fellow was simply enjoying the snow rather than doing anything too serious. He wove in and out of cover, posed for me and eventually bounded into the woods in search of greener (or whiter) pastures.

Pine Marten, American Pine Marten, Chichagof Island, Hoonah, Southeast Alaska, Martes americana
American Pine Marten on Chichagof Island near Hoonah, Alaska.



R. Flynn and M. Ben-David. 2004. Abundance, prey availability and diets of American martens: implications for the design of old growth reserves in Southeast Alaska. U.S. Fish and Wildlife Service Grant final report. Alaska Department of Fish and Game.

Ben-David, M., Flynn R.W., Schell D.M. 1997. Annual and seasonal changes in diets of martens: evidence from stable isotope analysis. Oecologia. 111:280-291.

Buskirk, S.W. 1983. The Ecology of Marten in Southcentral Alaska. Doctoral Disertation. University of Alaska Fairbanks.


Davis, Mark H. “Post-release movements of introduced marten.” The Journal of Wildlife Management (1983): 59-66.


Paul, T. 2009. Game transplants in Alaska. Technical bulletin #4. 2nd Edition.

Schoen, J., Flynn R., Clark B. American Marten. Southeast Alaska Conservation Assessment. Chapter 6.5

Ashbrook, F.G. Blue Fox Farming in Alaska. Accessed : https://archive.org/details/bluefoxfarmingin1350ashb 10/27/2016