Fossils: Window to the past

Wax & Asphalt

What are wax and asphalt?

Wax and asphalt, used as preservatives, are minute parts of the entire realm of fossilization. Wax is the most difficult of all the old materials to deal with. Fortunately, waxes were rarely employed as consolidates, except for elephant's teeth and tusks. Instead, they were widely used as adhesives and sometimes for restoration purposes. It seems that almost every type of natural wax have been used one time or another, either alone or in mixtures with others. Natural paraffin, a type of wax, is almost as effective (as a preservative) as ice. For example, in 1907 the head, forelegs, and a large part of the skin of a woolly rhinoceros were dug from a paraffin mine in eastern Poland. Nonetheless, paraffin wax was one of the least widely used form of wax for preservation. The most widely used wax used as a cement is yellow and brittle due to a high content of carnauba wax. The positive thing about carnauba wax is that it can be scraped off a joint or picked off with needles.

Asphalt, on the other hand, preserves only hard parts, such as bones, teeth, and the shells of insects. Vast numbers of these have been found in asphalt deposits of California, especially those now enclosed by Hancock Park in Los Angeles. In Hancock Park, an exhibit allows visitors to walk into a pit and examine fossil bones as they still lie in the tar. One of the major collecting site of this sort of fossilization is the La Brea tar pit in Los Angeles. This place is so well known that it now has its very own museum. From this very tar pit, thousands of bones, complete skeletons, even insects, leaves, and flowers, have been recovered.

The interesting thing about tar pits is the sequence in which the organisms were retrieved. The pattern of the positions of different organisms found in these tar pits paint a story of how these organisms have come about to get caught in the tar pit and become fossilized. First, a certain animal, usually a prey to some predator, would become mired in the tar pit as they come to drink. Then the predators that come to attack the helpless animals would themselves become stuck. Finally, all would sink slowly into the dense oil, which would keep their bones perfectly preserved. Therefore, the trend in the tar pits is that the prey would usually be found at a lower level than that of the predator.