- Infacol – if it’s good enough for babies, it’s good enough for ammonites. Christian Baars.
- The joy of steel: How to master your awkward fossil in the field. Nigel Larkin.
- Mechanical and chemical preparation methods used on the lower Eocene cementstone concretions from the Mo-Clay of northern Denmark. Frank Osbaeck.
- Preservation potential of elasmobranchs. Trine Sørensen.
A project to conserve, cast and repackage a collection of over 160 Jurassic ammonites from Dorset is currently being undertaken. The specimens are all cited and figured and include holotypes and paratypes. They had been previously consolidated with the acrylic resin Bedacryl, and some are embedded in plaster. The Bedacryl has become tacky with age and attracted dirt and dust. Pyrite is present in the rock and some ammonites are affected by pyrite decay. The specimens were cleaned, treated for pyrite decay if required, reconsolidated with Paraloid B72 and re-packaged. Due to the scientific importance of the collection, casts were made to ensure a record of the morphology should any further deterioration occur. Following re-consolidation, silicone moulds were made of the specimens. The intricate nature of the moulds made casting more difficult than originally anticipated. Jesmonite was used for the casts but it was difficult to avoid the formation of bubbles. After some experimentation it was found that adding some Infacol (“formulated to relieve wind, infant colic and griping pain”) significantly reduced the number of bubbles in the casts.
Nigel R Larkin
Occasionally, fossils can be extremely big, very heavy, or horribly fragile. Sometimes they may present all three problems at once - the most problematic of which is fragile - and getting them from the field to the lab can be a challenging process. Polyeurathane foam jackets are a quick but messy solution and should no longer be used on health and safety grounds. Plaster jacketing is a well known and very useful technique but on its own is not always up to the job. Splints are frequently added to plaster jackets, but often in an ad-hoc manner. A very secure method is to bolt together a rigid cage of channelled galvanised steel around the specimen in the field and secure it sturdily to the plaster jacket. This gives rigidity in three dimensions, protects vulnerable elements and provides specific and secure places to attach cables or straps to a crane. The channelled steel and appropriate nuts and bolts do not rust, can be cleaned and stored indefinitely and re-used almost endlessly. Most importantly, if assembled competently the structure will allow a very large, heavy and fragile specimen to be lifted and transported much more safely than would otherwise be the case.
For five years Museernes Bevaringscenter in Skive have worked on several rare specimens from the Mo-Clay Formation of Fur and Mors resembling the fauna of the London Clay Formation. Foremost an almost complete tarpon (115cm), one of the best preserved in the world, which was prepared combining acid and mechanical methods. To start with the specimen weighed a tonne. This specimen's matrix was in part extremely delicate, and would break down if water or acid was applied. The skull of the tarpon is 3D preserved and due to a fracture down the middle presents a fully prepared brain cavity. It went for the exhibit after 1 1/2 years of preparation. The new preparation of an old specimen of a two meter long leatherback turtle has yieled many new details as well as possible soft tissue structures. Lastly I will present two small turtles with exceptional preservation- the last one with ossified horn covering of the skeletal plates.
Different parts of the elasmobranch skeleton are unevenly represented in the fossil record. Fossilization of different types of tissue depends on structure and chemistry of the tissue and of a number of taphonomic factors. A single vertebra and fragments of gill rakers of a shark, Cetorhinus sp., from the Late Miocene Gram Formation was examined for variations in mineral contents within the tissues and in the surrounding clay sediment. During preparation a systematic, visual description was performed and samples were taken for microscopy and XRD mineralogical analyses and for SEM/EDX and EMPA geochemical analyses. The vertebra and gill rakers are composed of apatite-minerals containing fluorine with resemblance to recent shark skeletons. Apatite in the sediment below the vertebra may in part be due to dissolution. Authigenic minerals such siderite, calcite and Mg-calcite are present in both fossil and sediment in a pattern related to the vertebra. Pyrite is evenly distributed. Several parameters increase the preservation potential of the shark. These include the precipitation of carbonate-concretions around and within the vertebra, secondary calcification of the vertebra, the closely packed structure of the surface of the gill rakers, a calm sea, a high sedimentation rate and the right geochemical conditions.