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ANNOTATED NOTES FROM SUMMER, 1998 FIELD INVESTIGATIONS IN ALASKA

Saturday, June 13: Josh Been and I (Ager) flew on an early morning flight from Denver, Colorado to Seattle, Washington, then boarded another plane for a flight to Anchorage, Alaska. Then we had another change of aircraft for our final flight of the day to Fairbanks, Alaska. We arrived in mid afternoon (having gained two hours from crossing two time zones). We picked up our two rental vehicles (Ford Explorers) that we will need to haul heavy equipment, then drove to our hotel, where we met up with Larry Phillips, who had arrived a couple days earlier to participate in an aircraft safety class.

Sunday, June 14: Nice sunny, warm day in Fairbanks. We drove out to a placer mine near Ester, Alaska, a few miles west of Fairbanks to revisit exposures of late Pleistocene age sediments that Dan Muhs (USGS, Denver) and I had sampled in some detail in 1996 and 1997. Dr. Troy Péwé met us there, along with Dr. Glenn Berger from the Desert Research Institute in Nevada, Dr. Jim Begét and Dr. Paul Matheus from University of Alaska, and several graduate students. We used this opportunity to discuss what Muhs, Begét, and I had found during our previous two seasons of field work at this site. Troy Péwé was interested to hear that we had succeeded in obtaining excellent pollen samples from the interglacial forest bed (Eva forest bed) described previously by Troy in several publications, most recently in a 1997 Geological Society of America Memoir.

I had tried unsuccessfully on several occasions over the years to extract usable fossil pollen assemblages from the frozen and thawed loess sections in interior Alaska. I keep trying because these loess sections often contain what may be the most complete record of Quaternary sediment deposition available, and some sections appear to extend back into the mid-Pliocene. These sections are difficult to interpret because of erosional unconformities, slumping and other complications, but they do often span very long time intervals.

Most samples I had previously collected for pollen at Fairbanks area exposures and other loess sections in Alaska turned out to be barren of pollen and spores, or nearly so. Pollen and spores can be preserved for millions of years if it is buried quickly and protected from oxidation. Loess deposits (wind blown silt) tend to thaw and dry out readily, so the pollen that was originally buried in them is usually destroyed by oxidation. Our success in 1997 was because of a new sampling strategy we experimented with. We spent a lot of time (a week) excavating a large area of exposure that had slumped and which had become heavily vegetated since mining ended decades ago. With a large area exposed (instead of a narrow trench that exposes very little lateral extent of the sediments) we were able to find thin (often less than a centimeter thick), discontinuous layers and lenses of peat and organic silt within the loess. We sampled those peaty layers and when we processed them in the laboratory back in Denver, most contained pollen in quantities that permitted quantitative analysis of the pollen flora...thus allowing us to reconstruct the past vegetation types associated with that part of the deposit.

As a result of our success at extracting good quality pollen samples at the placer mine we were able to document evidence for a well-developed boreal forest in interior Alaska during the last major warm event that preceded the last glaciation. The pollen data also indicate that the warm interval was followed by a cold period during which boreal forest was replaced by tundra rich in sedges. That cold period was then followed by a somewhat warmer interval during which a mixture of tundra and restricted boreal forest communities co-existed in the area (forest-tundra or gallery forests in lowlands with upland tundra). That sequence seems to match up with known temperature oscillations associated with part of the last interglacial (perhaps representing marine oxygen isotope Substages 5e (warmer than today), Substage 5d (cold interval associated with expanding glacial ice), and Substage 5c (a warm interval, but probably not as warm as today).

We were also able to document some vegetation changes that occurred during the mid-Wisconsinan interstadial, an interval that was generally warmer than during glacial climates, but generally cooler than during the Holocene (the past 10,000 years of interglacial climates) or during the previous major interglacial that occurred about 130,000 to 120,000 years ago.

Some of our recent observations are somewhat at odds with what Péwé and his co-authors described from previous visits, such as the relative positions in the section of the Stampede tephra, the Dome Creek tephra, and the Old Crow tephra. It remains unclear how to explain the differences in what we see now, vs. what was exposed and described in previous years. These sections have been slumped substantially during thaw episodes, and there are large rotational slump blocks obvious in some areas, so it is quite possible for stratigraphic relations to become very confusing, and change over time as erosion and slumping take place. It was an enjoyable rendezvous with Troy and all the others, so we were glad that we had been able to find time to meet with them at the mine.

We spent the latter part of the day buying final supplies we would need while camping in eastern interior Alaska. We had to buy enough food for about 10 days, just in case weather prevents the helicopter from coming back to get us. That evening at dinner in Fairbanks I met with Judy Goettcheus Wolfe, a graduate student from University of Alaska who has been working with Dave Hopkins on a very interesting Ph.D research project on Seward Peninsula. She is reconstructing the full-glacial landscape and vegetation on northern Seward Peninsula based on plant macrofossils, pollen and other evidence preserved under a volcanic ash layer deposited about 17,000 years ago. We discussed her research results and how my data from St. Michael Island may be useful in supporting some of her interpretations of central Beringian environments. I brought with me from Denver a copy of my pollen data from St. Michael Island for Judy to work with so she can compare it with the pollen data from her site.

Monday, June 15: Phillips, Been and I spent a very busy day in Fairbanks, picking up our 1500 lbs. of air freight at Fairbanks airport, and hauling it all over to a mini-storage facility we had rented space in. We unpacked the shipping crates and managed to get all our gear into our two rental vehicles. We locked up our air freight containers in the storage unit so we can retrieve them later on to ship our gear to Ketchikan. We picked up two satellite telephones that we rented in Fairbanks, so that we could communicate with our base camp in eastern Alaska. Communication with the outside world is worth its weight in gold if someone gets injured or ill.  The telephone systems we rented are heavy, about the size of an old portable typewriter. Newer models will no doubt be much lighter weight, and eventually, much smaller.

Tuesday, June 16: We spent the morning shopping for a few fresh grocery items and ice for the cooler, then headed towards eastern Alaska via the Tanana Valley. It took us about 9 hours to drive to our base camp in the Fortymile River country (via Tok, in the upper Tanana Valley, then up the Taylor Highway). We arrived about 9 p.m. at the camp owned and operated by Larry and June Taylor, who reside there year-round (even when winter snows shut down the Taylor Highway for many months). Several of their rental cabins were occupied already by other USGS geologists from Denver and Anchorage, but we found two empty cabins to move into for the next couple nights. We are sharing the base camp and a helicopter with the USGS field party from Denver (Minerals Program), and scientists from the State of Alaska. This is a great place for a base camp, in a beautiful setting, and the facilities are comfortable, rainproof, and mostly mosquito proof. The Taylors provide meals for all of us, and that makes life easier. We will be eating our own cooking soon enough! Overnight temperatures dropped to 34° F (1.1°C) with some heavy rain. It was very lucky we were in cabins on this night. The area around the camp is pretty typical boreal forest of interior Alaska, with mostly white and black spruce, aspens, balsam poplars, willows, alders, and paper birch.

Wednesday, June 17: We unloaded our trucks at the base camp and sorted out all our gear into various bags and containers so we could get our equipment into three loads for helicopter transport. We tagged each bag with a color coded tag according to its priority for going into our field site. That way we made sure that the first person didn’t end up in the wilds without food, a sleeping bag, a tent, a first aid kit, and a rifle with ammunition. Any number of things can go wrong that would prevent the helicopter from coming back right away. We also weighed each bag and marked the weight on each tag so we could make sure the helicopter load was within safety limits. The afternoon turned rainy so we had to get all the gear under tarps. In the afternoon we drove to Chicken, an old mining community, to look at the placer mining operations and get fuel for one of our trucks. By mid afternoon the weather was deteriorating and we drove back towards Forty Mile through rain squalls. We arrived back at base camp late in the afternoon. In the interim, the helicopter had arrived late in the afternoon, too late to make any trips out to our study area near Mt. Harper. We met the pilot, Joe Trudeau, and he seems like a good guy and highly experienced pilot. He flew in Vietnam 30 years ago, so he has a lot of flying experience, and a lot of it is within Alaska.

Thursday, June 18: A Minerals team crew flew out to one of their study areas in the helicopter early in the day to get dropped off. When the helicopter returned to base camp around 10 a.m., we helped the pilot refuel, then loaded up our most essential gear (e.g., food, tents, first aid equipment, sleeping bag, rifle) for the first flight into our study area.

The coring operations we plan require a lot of gear, which is both bulky and fairly heavy. We have about 1500 lbs. (680 kg) of gear in total, including camp gear and food, so it will take 3 trips to get all of us and all the gear into the lake. I flew in on the first flight, since I knew how to find the lake we wanted to sample. It is a moraine-dammed lake that I had first seen during a one-day helicopter reconnaissance flight in 1982 with Florence Weber. The site is of great potential interest to us because little is known about the history of climate changes and ecosystem changes in the Yukon-Tanana Upland of eastern interior Alaska. There are few lakes in the region that are likely to contain more than a few thousand years of history, so this particular lake, in the Eisenmenger Fork of the upper Goodpaster River looked particularly interesting. The moraine that dammed the lake was formed by a glacier at least 75,000 years ago, and perhaps 135,000 years ago. So the hope is that we will be able to recover a very long history of environmental changes that would apply over a large area of eastern interior Alaska and western central Yukon Territory.

The helicopter flight from Fortymile base camp to the vicinity of Mt. Harper was very interesting, since the route travels over a great expanse of wild country, with boreal forest- covered valleys and lower slopes, and rounded bedrock ridges covered with frost shattered rock, patches of alpine tundra, solifluction lobes, and old caribou trails. As we approached the vicinity of Mt. Harper I began to get concerned about whether we would be able to get through the rugged mountain passes that are about 5000 feet (1500 meters) high, because the cloud cover near the mountain was hanging at just about that altitude. We flew towards several possible passes and the pilot backed off because of low cloud cover. It would be very dangerous to fly into clouds and be unable to see where we are going while surrounded by steep mountain walls. We flew over one of the alpine lakes I had seen on air photos and it is surrounded by talus and tundra vegetation.

This alpine lake may contain an interesting pollen record, but it probably only goes back to maybe 13,000 years ago. We are hoping to get a longer record from our other lake. We finally squeaked under the clouds through the pass just north of Mt. Harper and down into the glacial valley that leads into the upper Eisenmenger Fork area (a tributary of the Goodpaster River system). The upper valley looked pretty bleak, with steep rock cliffs, talus piles, moraine remnants, small streams, and patches of tundra vegetation. We followed the valley down until at last the unnamed lake we hope to core came into view in the distance.

As we circled the lake to search for a landing site, we saw three moose (two cows and a calf), one of which was standing in the shallows of the lake. Our pilot decided that the trees around the lake were too closely spaced to allow him to safely land near the lake, so we scouted around a bit and decided to land on a gravel bar along the Eisenmenger Fork, a bit southwest of the lake. We came in for a landing, settled right at the water’s edge, and I got out and began to unload about 600 lbs. (270 kg) of gear. We had some of the longer parts for the coring platform inside of ballistic nylon bags tied with bungee cords to the "baskets" on the struts below the doors, on the.outside of the helicopter. So I got those undone and dragged off onto the gravel bar. I moved away from the helicopter and he took off to fly back to base camp for another crew member and another load of gear. After the sound of the helicopter faded away, the main sound was the loud roar of the creek. It is only a few feet deep near the gravel bar, but it is flowing swiftly through a series of rapids and makes a lot of noise. I loaded the rifle just in case a bear with a bad attitude happens along (unlikely), then I began sorting out our gear. I found a place to set up our cook tent, and then I began setting up tents for us to sleep in at the other end of the gravel bar, back behind a row of willow shrubs. There are few flat areas, and the gravel bar consists mostly of coarse gravel, so I hauled a lot of sand in a collapsible bucket to make a flat smooth surface for the tents. In early afternoon Larry Phillips arrived on the second helicopter flight, so we got busy unloading the gear and sending Joe back to camp to pick up Josh and the remaining load of equipment.

By the time Josh arrived in the evening we had camp pretty well set up and organized. We hiked up to the lake to check it out, and we realized that it is a pretty good hike to get there from camp, considering that we will have to haul about 1200 lbs. (540 kg) of equipment up there. The lake is about 25 meters (80 feet) higher than our camp site, and the indirect route we took to the lake shore is probably 500 meters from camp. It will take a lot of trips. Fortunately I brought along a couple of sturdy pack frames, so we will be able to strap on some of our outsized loads of coring gear. The most unwieldy loads are the pontoons, the inflatable dinghy, the aluminum frame parts for the coring platform, and the pieces of the deck, some of which are more than 1.5 meters long.

This small lake (roughly 70 hectares in area) has a very limited catchment basin with no inflowing streams. Therefore it probably receives very little sediment, so even a few meters of sediment may represent a long period of time. The most recent glacial event during the late Wisconsinan (Oxygen isotope stage 2, ca. 26,000 to ca. 13,000 yrs ago) was cold and dry, and the glaciers that formed in the Mt. Harper area were of limited extent. That glacial advance did not reach as far down valley as this old moraine. So this lake may contain a record of glacial conditions in this area, as well as what has happened during the past 13,000 years of postglacial warmer climates. But often old lake basins in interior Alaska yield shorter records than they ought to contain because most lakes dried up during full glacial times, when the climate was both colder and drier in this region. If that is the case here, we will probably only get maybe 15,000 years of record. My hope is that we will get a much longer record than that. The lake area is surrounded by rather open boreal forest, and on the nearby valley slopes trees become sparse and interspersed with talus and patches of shrub tundra, willow thickets, and above that, alpine tundra communities that generally cover only a portion of the ground surface. The lake is at about 3000 feet (914 m) altitude, a few hundreds of feet below the regional altitudinal tree limit. Tree limit varies quite a bit, however, depending on slope exposure, protection from wind, soil conditions, moisture availability and perhaps other factors. During the helicopter flight in I saw stunted isolated spruce trees growing at or above about 1200 meters (ca. 4000 feet altitude).

We cooked up a good dinner on our propane-fueled camp stove and enjoyed the evening sitting next to this wild and roaring creek in this very remote valley. We are about 70 miles (112 km) from the nearest road (Taylor Highway). All around camp there are steep morainal hills that are part of the terminal moraine complex that Florence Weber mapped as the Eagle glaciation. She currently thinks the Eagle glacial event may be equivalent to the Delta glaciation in the Tanana Valley (equivalent to marine oxygen isotope stage 6?). If she is correct about the age of the moraines, then our lake may contain a very long record...at least in theory. After dinner I tried out our satellite phone to check in with Larry Gough (USGS, Denver) back at the base camp. We made contact at the pre-arranged time and the phone worked pretty well, although it took a couple tries to get through. We had to haul it up to the top of the moraine behind camp to get into a position to pick up the satellite, low on the horizon to the southeast. It was great to know that we had a way to communicate with the outside world if we had an emergency.

The sound of the creek next to camp is pleasant, but the negative side of it is that we may not hear the sounds of a bear tearing up our cook tent in the night, since our tents are a couple hundred feet from it (for safety’s sake). Our food is in bear-resistant containers but a determined bear would eventually break into some of them, given enough time. There is no place near camp where we can easily store all that heavy food off the ground, which is the safest way to protect it from critters. When I finally got into my sleeping bag, I had some trouble sleeping, in spite of being very tired. I was not yet used to having so much light late at night (something I have to get used to every year), and the sound of the creek roaring away nearby, plus my concerns about possible bear problems made it difficult to get to sleep. I was also thinking about all we had to do tomorrow, and whether the lake was going to give us the long record I was hoping to find here.

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U.S. Department of the Interior, U.S. Geological Survey
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