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Outcrop of the Great Northern Coal Seam at Catherine Hill Bay

Catherine Hill Bay
Teralba Conglomerate in cliff above Great Northern Coal Seam
Great Northern Coal Seam
Dolerite dyke intruding Bolton Point Conglomerate
Catherine Hill Bay
Teralba Conglomerate in cliff above Great Northern Coal Seam

Catherine Hill Bay

Latitude -33.159936, Longitude, 151.631069 (at the Jetty)

Located in the Hunter Region of NSW, nearest town Catherine Hill Bay

Source: Field Geology of NSW, Mineral Resources NSW Authors Brannagan & Packham

Source: Geological Survey of New South Wales, Bulletin 26

Source: Herbert, C., 1983. Geology of the Sydney Basin 1:100000 sheet 9130. New South Wales Department of Mineral Resources, Sydney

Link to Detailed Map

Catherine Hill Bay was an important coal mining and port facility in the 20th Century. The jetty and disused coal washery used in mining processes are still extant on site. The adjacent village is also an important example of a company-built town, constructed to provide housing for workers in a then remote location.

Geology

Catherine Hill Bay lies in the northern reaches of the Sydney Basin - a major structural basin containing a thick Permian-Triassic (290 Ma - 200 Ma (million years old)) sedimentary sequence that is part of the much larger Sydney-Gunnedah- Bowen Basin.

The geology of the Sydney Basin is best described by Herbert, (1983). It is predominantly the result of sedimentation and phases of earth movements. The underlying structure of the Basin was laid down during the Permian and earlier geological periods under marine and marshy conditions which, due to major earth movements, produced the sandstone and siltstone formations and intervening coal measures lying at considerable depths underneath the city of Sydney. These coal measures stretch north to Newcastle and outcrop in cliffs along the Hunter Coast.

The rock sequence in the Catherine Hill Bay area marks the transition from coal-bearing Permian strata (250-270 Ma) to barren fluvial Triassic sediments. In particular, the Moon Island Beach Subgroup of the Newcastle Coal Measures (Late Permian), together with basal units of the Triassic Narrabeen Group, outcrop in the Catherine Hill Bay area ( Ziolkowski 1978, pp3-8).

The Newcastle Coal Measures are located adjacent to the New England Fold Belt, which was the dominant source of sediment deposited into the Sydney Basin throughout the Permian Era. Deformation and uplift of the New England Fold Belt in the late Early Permian led to the transformation of the Sydney Basin into a foreland basin. Erosion of the active New England Fold Belt led to the deposition of sediments into this basin. The large volume of sediments eroded from the topographically active New England Fold Belt led to a prolonged regressive sequence of deposition forming the Newcastle Coal Measures.

The Newcastle Coal Measures at Catherine Hill Bay

At low tide you can walk under the jetty near the disused coal washery to gain access to the rock platform. On the cliff face you will observe the Great Northern Coal Seam, sandwiched between the Teralba Conglomerate on top and the Bolton Point Conglomerate below.

Also at low tide, you can walk to the wave cut platform where there are a number of Dolerite Dykes intruding the Bolton Point Conglomerate Member. Close observation of these dykes will show a dolerite centre and chilled margins on either side where the hot magma made contact with the cold conglomerate.

Additionally, you can walk south around the headland past Desoto Inlet and down onto another wave cut platform. Head further south along Moonie Beach and, just before Flat Island, there is a large fossilised tree which has two trunks giving the impression it is the fork of a tree.

Cross the sand dune onto Ghosties Beach to see several more fossilised trees. At the cliff face at the back of Ghosties Beach, you can see the stratigraphy with Munmorah Conglomerate at the top of the cliff and white sandstone below, overlying the Vales Point Coal Seam. Underlying the coal seam is the Karignan Conglomerate Member lying above the Wallarah Coal Seam that is obscured by vegetation and sand. Underneath is the Great Northern Coal Seam separated by a metre of material.

Further down the beach there is a sea cave eroded along joint planes. There are many concretions in the sandstone cliff along with examples of cross bedding and cut-and-fill gravelly stream beds. A number of fossilised branches that have rolled down these ancient streams can be found dotted around the cave entrance along with the Wallarah Coal Seam which is at the base of the Karignan Conglomerate Member.

Getting There

Catherine Hill Bay is a small coastal town, 26 kilometres south of Newcastle and 100 kilometres north of Sydney. It is located on the Wallarah Peninsula, bordered by Lake Macquarie to the west and the Tasman Sea to the east.

Access the route from Flowers Drive in Catherine Hill Bay. Park nearby and walk under the jetty to the headland or go to the end of Montefiore Road and walk down to the beach below the disused coal washery. Remember it is best viewed at low tide.

Allow 1.25 hours to walk the rock platform and examine the coal seam and dyke. If walking to Ghosties Beach via the coastline the distance is about 4.25km each way so allow much more time. Make sure you take a hat and sunscreen.


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