Burrowed ground

October 10 to 18
After the conference I went by plane to Neuquén, in central Patagonia, for a week of fieldwork and prospecting. While not terribly remote today, Neuquén was an outpost when the first fossils were collected in 1890 from rock outcroppings in and around the city. In the last 15 years Argentinean scientists have begun to collect, describe and publish on the vast resource contained within their own country. I consider myself lucky to be invited to participate in their projects.

Behind Universidad Nacional de Comahue are a series of small cliffs that are approached by walking across a wide, flat and seemingly featureless expanse of hard, pinkish sandstones. The diverse and spectacularly well-preserved vertebrate fauna of Neuquén (snakes, birds, velociraptor-like dinosaurs, long-legged crocodiles and titanosaurid sauropods) are found in these sandstones. On first examination, the sandstone units seem full of very unusual concretions. The grains of included sands are extremely coarse, very angular and rough, and very well cemented together.

I hunted around a bit, located a nicely weathered creek bed and discovered perhaps the single most important palaeoenvironmental indicator I could have hoped to find -- the concretions were not concretions, but trace fossils of burrows! Thousands upon thousands of burrows coursed through the sandstones above and below the rocks containing the Cretaceous vertebrates.

Animals that burrow into sediments are extremely informative for diagnosing the surrounding environment. Shrimp burrows are made in marine habitats. Likewise, insect burrows are only made in terrestrial environments. Identification of the burrow-makers would offer a specific set of indicators about the palaeoenvironment in which the snakes, birds, dinosaurs and crocodiles had lived. Because I'm not a specialist on fossil burrows, I made no positive field identification of the burrow-makers. After returning to Ottawa, associates at the University of Alberta, Murray Gingras and Thomas Saunders, tentatively identified the burrow-makers as insects, and most probably bees! The possibility that the Cretaceous deserts of Patagonia had swarmed with hundreds of thousands of bees set my imagination spinning. Gingras and Saunders also suggested that some of the preserved burrows might be root casts -- probably from the plants whose nectar the bees collected.

The Rio Negro crosses through this portion of the Patagonian desert and provides a surprise of lush green vegetation in the middle of the Alpataco scrublands.

The new specimens of Dinilysia patagonica that I had seen in Buenos Aires had been found 27 km from the university on a small goat farm along the Rio Negro, close to a river crossing called Paso Cordoba. Out in the middle of the northern Patagonian desert, the rocks are exposed for miles and miles. The rocks give way in view to small pink flowers on tiny little plants, and miles and miles of thorned Alpataco bushes.

I rented a four-wheel-drive truck, and the museum lent me the services of Pablo Possé as driver and guide. Pablo, whom everyone calls Paul, is now one of my closest friends, and proved to be an excellent field assistant and most competent driver. We explored half of central Patagonia in just a few days.

I was still thoroughly confused by the mysterious burrowed rocks, and complained to Paul, "This reminds me of my favourite axiom: Each answer only rattles the question harder!" Because I was one of the first scientists to study the rocks of the Rio Colorado Formation on the south side of the Rio Negro, the questions I could answer only created more difficult questions.

A typical day in the field requires particular equipment. I took: a pogo stick (a 1.5-m broom handle marked for measuring rock layers), field notebook, camera equipment, rock hammer, specimen bags and a pair of shorts. Days usually started out cold, as October is the beginning of spring in the Southern Hemisphere, but would heat up to 30-35°C by noon or so. Using the pogo-stick, Paul and I measured up the side of a cliff or gully. We made notes on the changing rock types and the relative thickness of the layers, collected rock samples, noted the presence of fossils and the type, photographed the rocks, and then moved to the next location. Although we didn't find any snake, theropod, or bird fossils, the fossil bones of giant sauropod dinosaurs were common. I did find the weathered skull of a crocodile!

We collected a lot of data on sediments and trace fossil of animals. Considering the difficulty of interpreting the palaeoenvironment, this information proved to be key data. The rock layers alternated between burrow units and thick, featureless sandstones. These featureless layers were likely formed when a big storm (probably a sandstorm) deposited sediment on the burrowing community. The units of burrowed sandstone cover large areas and are very thick, suggesting the animals doing the burrowing had a long period of time to develop their burrow systems.

October 19 to 24
With my trip nearly over, I went to the coastal city of Mar del Plata to spend the next week writing papers and studying the new snake fossils with Dr. Albino.

In my free time I learned many things, including how to cook an asado, the Argentine equivalent of a barbecue, but far more sophisticated.

Once back in Ottawa, I will have much work to do with the data collected here, including the planning of return trips to assemble a more complete palaeobiological picture of the Cretaceous of Patagonia.

Palaeontology is a multifaceted science and fascinating livelihood that combines hard, physical labour; travel to spectacular and remote places around the world; problem-solving, writing, research, and teaching skills. While the job is all-consuming, the rewards are great.

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