March 13, 2006

Funded by the National Science Foundation Office of Polar Programs

Location: Latitude 63° 51.6' S, Longitude 54° 26.95' W

Air Temperature: -3.1°C

The Science

Geologists are a lot like landscape artists, except we try to reconstruct landscapes that existed millions of years ago. Our pallet is filled with a variety of tools, like paleontology and sedimentology, that help us with our reconstruction. Here in the Weddell Sea we are attempting to reconstruct the setting that existed a few tens of millions of years ago, before this part of the Antarctic continent was covered by ice. Obviously the photograph that goes with this journal article is not from Antarctica. I took it in a beach forest near Pucon, Chile on my way to Punta Arenas. But it could easily represent the landscape near Seymour Island 40 million years ago. We know this because of the fossil pollen and spores that have been found in sediments of this age. A few million years later, the climate of the region began to deteriorate as Antarctica separated from South America, its last link to a warmer world.

The Antarctic Peninsula would have been the last place on the continent to experience full glaciation. Imagine the changes that must have occurred as the Antarctic Ice Sheet grew and spread northward. It is likely that the last of the plant and animal survivors made their final stand in the northern Antarctic Peninsula. Competition for food and space was intense and only the hardy survived the increasingly harsh climate. The remaining forests were comprised of a single, scrubby little tree, Nothofagus, which still dominates the forests of southern Chile and Argentina. Giant penguins, up to 5 feet tall, may well have ruled the animal world, at least on land.

How long was the transition from temperate forests to ice caps and when did the continent become fully ice covered? The fact is we do not know because sedimentary rocks from the time interval between 40 and 20 million years are rare on the continent. During SHALDRIL we are attempting to recover rocks and fossils of this age. But, Antarctica does not give up its secrets easily. To date we have had to contend with continuously shifting sea ice that has caused us to abandon sites where the older strata were within a few meters reach of our drill bit. But yesterday our luck changed and we were able to remain on station long enough to core into older sediments. We knew from our first glance of the cores that glaciers did not deposit the strata we had sampled. In fact, every indication is that we had sampled an old river delta. As the core was still coming on deck the paleontologists worked frantically at their microscopes searching for fossils that might tell us the age of the deposits we were sampling. Finally the word came; the cores had sampled sediments that are between 36 and 31 million years old. What joyous news. We had filled a large gap in the continent's geological record, a time when the climate was clearly more hospitable to life. I cannot wait for the samples to arrive back in the states. There they will be examined by colleagues who will use shell material in the cores to obtain more precise ages of the strata. Palynologists (people who study fossil pollen and spores) will tell us what the vegetation was like. Other scientists will look at the clays and determine what types of soils existed and others will study the sediments to determine what the coastal environment was like at that time. And from this combined effort our painting will be created. This is our time machine that takes us back millions of years to times that even the best science fiction writers are unable to accurately capture. How lucky we are to be ancient landscape artists.

John Anderson

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