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Logging Tasks:
1) Describe what these conglomerate cliffs look like, including texture and colour.
2) Alongside the parking area lookup and identify what succulent can be seen on the HIGHEST ledge.
3) What is crushed aggregate?
4) What is the definition of an alluvial fan?
5) Optional - upload a photo of yourself and GPS with the rock formation of Queen Victoria in the background.
Please do not include any other conglomerate formations or cliffs in the photo.
This profile is the result of erosion. The road cuttings in the area are characterised by sheer cliffs. About 140 million years ago the Cape Mountains were roughly three times higher than today. A period of high rainfall then eroded them and the Enon Conglomerate was the result. Much of the Gamtoos valley is composed of this.
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments.
The geological strata of this area known as the Enon Formation were formed when boulders, pebbles, sand and clay were deposited in an early basin of the Gamtoos. The material was subsequently cemented together to form conglomerate consisting of reddish brown, coarse-grained conglomerate, typically of the quartzite and other hard rocks and hardly anything else. The Enon Formation was deposited in the form of alluvial fans by rivers draining the Cape Fold Belt mountains. In places the Enon conglomerate is quarried to produce crushed aggregate. It is a poor aquifer.
Alluvial deposits are formed in areas of high relief and are typically coarse-grained. At mountain fronts individual alluvial fans merge together to form braid plains and these two environments are associated with the thickest deposits of conglomerates. The bulk of conglomerates deposited in this setting are clast-supported with a strong AB-plane imbrication. Some matrix-supported conglomerates are present, a result of debris-flow deposition on some alluvial fans.
The Gamtoos River has a catchment area of 34,635 km². The name Gamtoos is derived from a Khoikhoi clan whose name was given by early Dutch settlers as "Gamtousch". Although the rainfall in the catchment area is low it supports a commercial irrigated agriculture in the lower catchment in which oranges, tobacco, citrus fruit and vegetables are grown.
Recognition and references:
Field guide to the Eastern Cape and Southern Cape Coasts by Roy Lubke, Irene De Moor, I. De Moor
wikipedia.org/wiki/Conglomerate_(geology)