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.