Her cold white coat preserves her charm

And the cold wind's chill keeps her fresh

But still she hides her many secrets

From those who know her best.

Time will never change her

For she's constantly renewed

The source of endless mystery—

Always sought and wooed.

—a poem by Harold Brown, seaman on the Private John R. Trowle

Day 19, 4 December, was a clear sunny morning, 7°F. We traveled across to Mt. Gudmundson from Skua Ridge without incident, pitching camp high up on the snowy foothill of that mountain at an altitude of 1480 meters. We turned into bed early that night, readying ourselves for what we expected would be a long day. Our plan was to find a safe route up to the top of Mt. Gudmundson and spend as much time as the weather allowed working on the mountain.

It was indeed another long day. The next five pages of my notebook are filled with details of the stratigraphic section on Mt. Gudmundson, measuring each layer of rock down to every centimeter of detail to record the subtle changes in sedimentology. Fraka, our resident sedimentologist, usually did this job but because she wasn't feeling well that day I volunteered to do the job. I thought it would give me good practice at being “a real geologist” once again, taking me back to my student days as a geology undergraduate when measuring and describing rocks was an integral part of my studies. By taking such de-

tailed measurements geologists can determine the changes in the environments in which the sediments were deposited. The layers can represent many sub-environments (called “facies”) within a large environmental system. For example, our Aztec Siltstone represents a large alluvial plain system within which we could readily identify individual river channels, lake deposits, sand bars, overbank flood plain deposits, and even ancient soil horizons. Only by such careful observation of how each sedimentary layer differs, by both its composition and sedimentary structures, can a geologist determine the change from one part of the environment to another, and get an understanding of larger scale regional topography. Very detailed studies are then done by cutting thin sections of the rocks (about 30 microns^★ thick) and examining their mineral composition and small-scale structures under a petrological microscope.

To the trained sedimentologist, even the types of quartz present in a single layer of sandstone can reveal a wealth of information about the topography of the ancient environment in which it formed. For example, if the sediment is largely composed of quartz grains derived from the erosion of volcanic rocks, then that means the land then had volcanoes in its highland regions, and volcanoes today signify crustal rifting and volatility, and these often have ore bodies associated with them. So, it was imperative that the new section be measured and studied centimeter by centimeter, and that adequate samples of the rocks be taken at the critical points where the sedimentology varied.

However, before we could attempt any “geologizing,” as Scott used to refer to it, our immediate mission for the day was to get safely to the top of Mt. Gudmundson. We could see through our binoculars that the colored layers of rock there appeared to be the fossiliferous Aztec Siltstone. Getting up Mt. Gudmundson didn 't look so easy as there was a very steep ice and snow bank forming a razorback up to the rocky outcrops. These formed steep-walled cliffs of sandstone.

On our first attempt we drove the skidoos straight up the steep slope as close as possible to the rocks, but it soon became too steep for safety, so we had to level off at this point and park the vehicles. Brian

suggested that we scale it in the regular way using mountain-climbing equipment, and that the two of us go up first to establish a safe route.

We donned our harnesses, roped ourselves together, fitted crampons to our boots, and each grabbed a batch of about twenty bamboo flagpoles. Brian led the way carefully up the narrow ice ridge. Each side of the sharp ridge formed a very steep icy slope. As we gradually eased up the mountain, the sides of the ridge became steeper and more distant from the rocks at the base. Towards the top of the sharp ice ridge there was approximately 300 meters of icy slope on each side of us, with large jagged rocks protruding at the bottom. Every step had to be carefully placed, so I followed in Brian's exact footsteps. In places we had to cut flat footholds with our ice picks. We placed flags along the route as we went.

On approaching the top, we encountered the vertical whitish-yellow cliffs of Beacon Heights Orthoquartzite. They appeared quite formidable at first glance, but by scouting around for a few minutes Brian soon discovered an easy climbing route around the side of the sheer outcrop that took us up above the 60-meter bluff onto the flat top of the mountain. While I stood happily on top of the cliff savoring the view, Brian quickly raced back down like a mountain goat to get the others. A short while later, Margaret, Brian, and I were standing there together. As Fraka still wasn't feeling well that day she remained back at the camp.

Step-like layers of alternating dark and light colored shaley rocks led to the summit of Mt. Gudmundson. The very top of the mountain, above these multicolored Aztec layers, was formed of a cap of about 40 meters of steeply inclined dark green glacial deposits. These are from the great Permian ice age that covered Gondwana some 290 million years ago, whose geological deposits are also found in Australia, India, and South Africa. Glacial deposits such as these are geologically very distinctive. Heavy rocks trapped in floating glacial ice drop as the ice melts, so the sediments formed below are usually a poorly sorted mixture of rocks of variable sizes and shapes in a matrix of finer grained muds and silts.

We felt the elation of every person who has ever been the first to climb any mountain, even though this was an easy one to scale and not very high at only 1950 meters! Standing on its peak gave us spectacular

views of the nearby Cook Mountains and the wind-strewn polar plateau to the south.

The rest of that morning we were kept busy measuring and describing a detailed geological section through the Aztec Siltstone. Logging this section, centimeter by centimeter, took me all of that day and part of the next day, but in the course of the work several layers rich in fossil fish remains were discovered. Brian assisted me by holding the measuring staff for each locality or chipping out specimens requiring hours of patient labor. Margaret found some very interesting trace fossils that day, so she spent most of her time measuring and describing them. Later in the afternoon I made a particularly good find, a complete internal cast of a large skull of the placoderm fish Bothriolepis. A good deal of hammer and chisel work was required to free it from its hard sandstone repository, but it was well worth all the effort. It was the first complete skull of a fish I'd found so far on the expedition. Moreover, the internal cast of the skull shows some of the most diagnostic features for the different species of Bothriolepis, so I knew at once that the specimen would be useful for identifying its exact species. We kept working on top of the mountain until about 8:00 P.M., and we all collected loads of great specimens. Our backpacks were bulging and heavy by this time, so we carefully headed down along the flagged route back to the camp, arriving just after 9:00

Fraka had spent the day resting in the tent and was feeling much better by the time we returned to camp. She was excited to hear about our day's work and agreed to join us up the top of the mountain the following day.

I awoke to a “warm,” hazy morning with the temperature at 18°F, and light winds blowing at six knots. Overhead hung a cloudy grey sky with the possible threat of snowfall. After breakfast all of us ascended the mountain and by working as a team we finished logging the section by mid-morning, now aided by Fraka's expert sedimentological eye. I then went off to collect fossils from each of the layers we had identified the day before. Many excellent specimens turned up that day, including more Bothriolepis. Some layers were quite rich in small fish remains, like the interesting double-pronged sharks' teeth and the fin-spines of acanthodian fishes.

Margaret was overjoyed to find a very rare “resting trace” of the creature that probably made the Beaconites traces, as it was sitting on top of one of these distinctive burrows. Such fossil burrows are known from many sites throughout the world, but never before had anyone found any actual fossil evidence as to what kind of animal might have made the burrows, so this was an exciting discovery. Having no materials on hand to make a cast of the trace, Margaret attempted to make an “ice cast” using her personal supply of orange juice drink. She first covered the trace fossil with a layer of thin wrapping plastic, then poured her thermos of orange drink over the top. She returned later that afternoon when it had frozen solid. Unfortunately, it broke apart when she tried to lift off the ice cast, so she had to content herself with just photographs and detailed sketches of the important discovery. We discussed the trace at length in the field, and agreed that it most closely resembled the body plan of a flat lobster-like crustacean, maybe a primitive relative of today's delicious Moreton Bay bugs (a small lobster-like creature indigenous to Queensland, Autralia).

The next morning felt almost hot when the temperature soared to 21 °F, with only a faint wisp of a breeze. In the sky some lenticular high-level clouds were suspended over the dark brooding Warren Range, about 60 kilometers away from our camp on the other side of the Mulock Glacier. It was time to make tracks, so we packed up camp and headed back to our depot at Seay Peak in the northern Finger Ranges, arriving in the early afternoon after a pleasant and uneventful sledge journey.

Our next task was to prepare our gear for the helicopter lift across the Mulock Glacier due to take place the next day. We had to make sure that all our specimens were carefully wrapped, labeled, and packed in wooden boxes for transport back to the base. Then every piece of equipment, including our food supply boxes, had to be accurately weighed so that we could tally the full weight of each underslung load. We did this using a set of small hand scales. The skidoos were to be underslung by the helicopters, so they had to be stripped down. We removed their fiberglass fairings, secured the steering mechanisms and emptied any remaining fuel out of their tanks. The bare sledges would be tied to the sides of the landing gear of the choppers.

The helos would also take “retro”—the term used for anything to be taken back to Scott Base. This comprised our samples collected so far, our rubbish bags and our ominous bag of frozen human waste. There's an interesting story about this subject told to me by Brian how a few years back the helicopter pilots used to keep their cabins nice and warm by turning the heaters up high. One time a helicopter came to transport a field party and take back their retro, which included a large plastic bag of frozen waste. Someone carelessly threw the bag in the helo behind the pilot's seat, and the crew commenced their long flight back to base with the heater blaring away inside their cabin. After a while they could smell something really awful and soon had a lot of unsavory brown slop swishing around their feet, as the bag had ripped apart and the waste material had melted from the heat. From then on, VXE-6 Huey pilots always arrived at such missions wearing thick warm clothing and refrained from heating up the cabins of their helicopters on trips back to base. The bags of refuse were stored at the base frozen outside near the sheds until we returned, when we would dispose of them by incineration.

That night we discussed the crossing of the Mulock Glacier. Not only did we hope to receive news from home when the choppers arrived, but we would be getting re-supplied with some fresh foodstuffs from Scott Base. It also signified the end of the first half of our field trip, our successful journey through the Cook Mountains from the Darwin Glacier at 80° south to the Mulock Glacier at 79° south.

After our airlift over the Mulock Glacier we would be able to start exploring the many mountain ranges and isolated outliers fringing the vast white plain of the Skelton Névé, where earlier VUWAE parties had collected superb fish fossils during the 1970-71 season. We were full of hope that new fossil localities would be found in the region during our explorations.

A new journey was to begin.