Cape Nelson is located approximately 13 kms from Portland.
The Cape Nelson State Park is located on Victoria's southwest coast. The State Park covers 243-hectares (600-acre). There is a 3 kilometer clifftop walk at this location, the Cape Nelson Lighthouse and part of the course of the Great South West Walk is also located within the park.
Cape Nelson is a peninsula of volcanic rocks overlaid by sedimentary rocks, dominantly limestone and calcarenite dune limestone. In the high, steep coastal cliffs there are several basalt lava plugs marking eruption points, and associated lava flows and tuff beds. These volcanic structures suggest that the capes are the eroded remnants of a larger volcanic system, the southern parts of which have been faulted (caldera subsidence) and / or eroded to form the arcuate Nelson Bay and Grant Bay. On Cape Sir William Grant, three unusual eruption structures (“The Wells”) exposed along the shoreline are the tops of small adventive or parasitic cones built on the flank of the larger volcano. They are seen in cross-section as plugs of volcanic fragments filling a near-circular pipe in basalt. Along the northern shore of Nelson Bay between Cape Nelson and Cape Sir William Grant is a thick sequence of sediments (Lower and Upper Nelson Bay Formation and Bridgewater Formation) filling a synclinal depression in the volcanic surface. Different styles of unconformable contact between these formations and mild deformation (folding) is evident in coastal cliff sections. The coastal cliffs here are among the highest on the Victorian coast and are exposed to very strong wave action resulting in impressive displays of wave break and reflection. 90 m; 90 m. National signifigance. The coastline exposed a rich variety of volcanic structures including the unusual parasitic cones known as “The Wells”. Along with Cape Bridgewater, it forms part of a distinctive volcanic complex which has no counterpart on the Australian coast.
This location is an outstanding site to study the details of volcanic processes in the early (Pliocene) phase of the Newer Volcanics Province. It is one of only three sites in the Newer Volcanics Province where caldera formation has been interpreted. The northern coastline has an excellent display of different limestone sediments and is an important stratigraphic site for tracing Plio-Pleistocene stratigraphy in western Victoria.
Calcarenite
Calcarenite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), carbonate grains. The grains consist of sand-size grains of either corals, shells, ooids, intraclasts, pellets, fragments of older limestones and dolomites, other carbonate grains, or some combination of these. Calcarenite is the carbonate equivalent of a sandstone. Calcarenites can accumulate in a wide variety of marine and nonmarine environments. They can consist of grains of carbonate that have accumulated either as coastal sand dunes (eolianites), beaches, offshore bars and shoals, turbidites, or other depositional settings.
PLEASE BE VERY CAREFUL AT THIS LOCATION. THERE ARE NO FENCES ALONG THE CLIFFS. DO NOT ATTEMPT THIS EARTH CACHE IN STRONG WINDS OR RAIN. KEEP A CLOSE EYE ON YOUR LITTLE ONES & DON'T GET TOO CLOSE TO THE EDGE.
Questions
Q1 Describe the rocks that you see at the Cape, looking down to the ocean.
Q2 How does the rocks differ to where you are standing?
Q3 It is one of how many sites in the Newer Volcanics Province where caldera formation has been interpreted?
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References ~ VRO & wikipedia