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Fossils and Geological Features Fossils and Geological Features

Overview

This stretch of the south east Australian coastline was once part of the coast of the ancient supercontinent of Gondwana. Early in the Permian period, about 295 to 269 million years ago (Ma), the sea level rose to cover the eastern edge of Gondwana. As a result, sediments rich in fossils were deposited on the seafloor along the coast. The resulting rock sequence, which is about 800m thick, is known as the ‘Shoalhaven Group’.

Animal groups that thrived at the time included colonies of Bryozoans (sea fans), Crinoids (sea lilies), and solitary Rugose corals (horn corals). All of these animals attached themselves to the silty bottom and fed by filtering food from the sea water. Animals that burrowed into the sediments on the seafloor included Bivalve Molluscs, similar to modern day pippis and scallops and two distinct groups of Brachiopods (lamp shells); Spiriferids and the often spiny-shelled Productids. Both groups of Brachiopods became extinct about 251Ma. Other animals that lived on the seafloor included spiral shelled Gastropods (sea snails), and several types of worms that left only their burrows, tracks or trails as ‘trace fossils’.

Burial of dead organisms by sediment must have been sufficiently rapid to limit bacterial decay of the soft animal tissues. Even where the hard calcium carbonate shells were subsequently dissolved by groundwater, their shape is often preserved as internal and external moulds in exquisite detail. The cavity formerly occupied by the animal’s shell was later in-filled by another mineral substance (such as iron oxide or silica) that was deposited from circulating groundwater. Such fossils are called replacement casts and they reflect the animal’s true shape but don’t preserve the internal structures.

Fossils and Geological Features - 16 species

Fossils Bivalve .... Desmodont (Desmodont Shell)

Bivalve .... Desmodont Barry Tomkinson at Wasp Head
Bivalve .... Desmodont Ian Stewart at Snapper Point
Bivalve .... Desmodont
Bivalve .... Desmodont

Fossils Bivalve .... Pecten (Pecten Shell)

Bivalve .... Pecten Lobster Jack's Beach Ulladulla
Bivalve .... Pecten

Fossils Brachiopoda Productida (Productid Brachiopod)

Brachiopoda Productida Lobster Jack's Beach Ulladulla
Brachiopoda Productida Charles Dove at Ulladulla Harbour
Brachiopoda Productida
Brachiopoda Productida

Fossils Brachiopoda Rhynchonellida (Rhynchonella Brachiopod)

Brachiopoda Rhynchonellida Jackie Miles at Dolphin Point
Brachiopoda Rhynchonellida Charles Dove at Ulladulla Harbour
Brachiopoda Rhynchonellida
Brachiopoda Rhynchonellida

Fossils Brachiopoda Spiriferida (Spiriferid Brachiopod)

Brachiopoda Spiriferida The Bommie Ulladulla
Brachiopoda Spiriferida The Bommie Ulladulla
Brachiopoda Spiriferida Lobster Jack's Beach Ulladulla
Brachiopoda Spiriferida
Brachiopoda Spiriferida
Brachiopoda Spiriferida

Fossils Bryozoan Fenestella (Fenestella Bryozoan or Sea Fan)

Bryozoan Fenestella Charles Dove at Ulladulla Harbour
Bryozoan Fenestella Ulladulla Harbour
Bryozoan Fenestella Ulladulla Harbour
Bryozoan Fenestella
Bryozoan Fenestella
Bryozoan Fenestella

Features Concretion (Cannon-ball Concretion)

Concretion The Bommie Ulladulla
Concretion Barry Tomkinson at Emily Miller Beach
Concretion
Concretion

Fossils Crinoidea (Crinoid or Sea Lily)

Crinoidea South side of Warden's Head Ulladulla
Crinoidea Lobster Jack's Beach Ulladulla
Crinoidea Jackie Miles at Dolphin Point
Crinoidea
Crinoidea
Crinoidea

Features Drop Stone (Drop Stone)

Drop Stone
Drop Stone
Drop Stone
Drop Stone

Fossils Fossilised Wood (Fossilised Wood)

Fossils Gastropoda (Gastropod or Sea Snail)

Features Glendonite (Glendonite)

Fossils Hexacorallia Rugosa (Horned Coral)

Hexacorallia Rugosa The Bombie Ulladulla
Hexacorallia Rugosa Jackie Miles at Dolphin Point
Hexacorallia Rugosa Lobster Jack's Beach Ulladulla
Hexacorallia Rugosa
Hexacorallia Rugosa
Hexacorallia Rugosa

Features Igneous Intrusion (Igneous Intrusion)

Features Tessellated Pavement (Tessellations)

Fossils Trace Fossils (Trace Fossil)

Trace Fossils South side of Warden's Head Ulladulla
Trace Fossils Ian Stewart at Snapper Point
Trace Fossils
Trace Fossils

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