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OPALISED FOSSILS FROM THE LIGHTNING RIDGE OPAL FIELDS
A wide range of opalised fossils are found on the Lightning Ridge opal fields by people mining opal. The region is one of the few places in Australia where a range of dinosaur fossils have been found. It also has produced the oldest monotreme (egg laying mammal) fossils in the world.
Most opal mines do not contain many fossils, and some have none. A wide range of fossils are found because there are hundreds of people mining for opal on more than 5000 separate mining claims in the region.
The main categories, or types, of fossils found by opal miners are;
| (1) Opalised plant remains | which includes plant stems and the seed bearing parts of
plants such as pine cones.
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| (2) Opalised animal remains | including shells, bones and teeth. |
| (3) Trace fossils | where the animal or plant has not been fossilised, it has just left evidence of its existence such as dinosaur tracks and fossilised worm burrows. |
DINOSAURS
Most of the dinosaur bones found on the Lightning Ridge opal fields are quite small and indicate that many dinosaurs smaller than a child. Commonly the bones are found isolated and scattered but in some cases articulated (joined) skeletons are found.
Types of dinosaurs that have been recognised amongst the opalised fossils from Lightning Ridge include sauropods (herbivores, walked on four legs), theropods (carnivores, walked on two legs) and ornithopods (herbivores, walked on two legs). Opalised teeth, bones and claws have been found.
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Dinosaur toe bone |
Dinosaur vertebra |
OTHER VERTEBRATES
Fossilised remains of turtles, crocodiles, fish, lungfish, plesiosaurs, pterosaurs, birds and monotremes have been found.
To date (March 2000) no marsupial or placental mammal fossils have been recognised.
The world's oldest known eel fossil consists of an opalised eel skull from the Coocoran opal fields.
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Monotreme jaw |
Plesiosaur teeth |
SHELLS
Various types of freshwater shells are found throughout the Lightning Ridge opal fields, although in the 1990s most shells came from the Coocoran opal fields where the majority of the professional opal miners were working. In most cases only the shell itself has been opalised, with the shell interior filled with sand or silt. Occasional exceptional specimens are found in which the interior of the shell is also composed of gem quality opal.
There is at least three species, or types, of gastropod (snail like) shells and at least twelve species of mussel shells known from the opal fields.
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Opalised gastropod shells |
Opalised mussel shell |
PLANTS
Layers of rock containing fragments of opalised plant stems, pine cones and seed pods are relatively common on the Coocoran opal fields. Complete and identifiable plant fossils are not common.
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"Pine cone" fossils |
Unidentified plant fragment - gem quality opal |
TRACE FOSSILS
Dinosaur tracks have been reported from a few opal mines in the area, as impressions in the "roofs" of tunnels. The opal miners generally excavate their tunnels in a comparatively soft layer of claystone rock that carries opal. This soft rock layer is overlain by a harder layer composed of sandstone, and it is in these sandstone layers where the tracks are found.
Fossilised worm burrows are quite common on the opal fields but in most cases they are not opalised.
MORE INFORMATION
The following book will provide more information on the fossils found on the Lightning Ridge opal fields.
Smith, E. & Smith, R. 1999, Black Opal Fossils of Lightning Ridge, Kangaroo Press, East Roseville, NSW.
The book is currently (Mar 2000) available through ........ DYMOCKS or ANGUS & ROBERTSON
A special thankyou to Robert A. Smith, the photographer and copyright holder for all images on this page.
