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Now the Hard Work Begins

Once the dust, or in our case sand, settles after each field season, the hard work of removing the fossil bones from their rocky tombs begins. There are many steps that may be necessary to prepare fossils, with the help of finds made at the Eric the Red West site in 2016. The bones and teeth of animals that lived and died in this area that is now part of the Early Cretaceous Otway Group (southwest of Melbourne), were swept into fast flowing streams and rivers, to be buried in the soft sandy sediment of the riverbed. Over time the soft sediment was compacted and buried to form a hard crystalline volcano-clastic sandstone conglomerate, which now outcrops along the Otway coastline from Dinosaur Cove to Lorne on the Great Ocean Road.

The sandstone conglomerate at the Eric the Red West site does not contain as many mud clasts as the Flat Rocks site on the older Bass Coast which not only makes it harder to break, but also harder to prepare. The sediments do not contain carbonate cement and, therefore, cannot be chemically dissolved using acetic acid. Preparation of the sandstone conglomerate involves mechanical preparation using pneumatic air tools such as the ARO air scribe. This tool is powered by compressed air which forces the tungsten carbide tip to move backwards and forwards very quickly, acting like a mini jackhammer.

Most of the fossil bones from the Eric the Red West site are less than 15 cm in length, which means that they do not need to be plaster-jacketed for transport. The fossil bones are discovered as the sediment, in which they are entombed, is broken down with a hammer and cold chisel. Unfortunately, this method also results in the fossils being damaged as the sediments are broken down and fossils within are exposed. It is, therefore, essential that all fragments of the bones are collected and labelled before they are carefully wrapped in tissue- and newspaper. In 2016 they were initially transported to Museums Victoria.

Once the boxes of fossils arrive at the Palaeontological laboratory at the Museum, the collections manager and his team of volunteer preparators begin the slow process of unwrapping the fossils, ensuring that the written information that accompanied each specimen is recorded and kept with each fossil. Before preparation can commence, the fossil has to be assessed, consolidated and if necessary, adjacent sections of rock and bone are glued back together again. Each fossil is unique, and no fossil is prepared in exactly the same way. It depends on how the fossil bone is exposed in the rock and how well it is preserved. Some bones are solid and break cleanly, others are fragile and break into many pieces. It is important to estimate the size and shape of the bone in the rock. A limb bone, which has broken through the shaft, revealing just a circular or oval cross-section, gives little indication as to the length of the bone or the angle at which it is lying in the rock. Some preliminary preparation may be necessary to ascertain the direction in which the limb is lying and the length of the shaft. Once the preparator has ascertained the size and direction of the fossil it is then possible to trim excess rock from around the specimen, which can considerably reduce the overall time involved in the preparation.

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