Fossils were discovered at this Limestone Rd site in 1875 but were not realised until 60 years later when they were studied by pioneering scientist Dr Isabel Cookson in 1935. The fossils were from a plant known as Baragwanathia Longifolia, which first appeared 415 million years ago. It is thought to be the first example (and oldest record) of vascular plants that made the transition from life in the water to life on land and therefore the fossils found at the site are of international significance. The site is therefore listed as a national heritage place.
The Silurian Baragwanathia Flora Fossil Site - Yea (Barclays Cutting) exposes well preserved specimens of Baragwanathia longifolia and a range of other plants occurring as part of a floral assemblage in graptolite-bearing beds. This rich fossil deposit of some of the earliest known vascular land plants is well recognised as being of international significance. The plant fossils provide evidence of the dramatic evolution and development of vascular plants that occurred during this time, particularly the adaptation of plants from the sea to the land. B. longifolia is almost exclusively found in the Southern Hemisphere and these fossils may indicate that land plants developed first in the Southern Hemisphere. The presence of graptolites confirms the Late Silurian age of about 415 million years. The Yea site has played a central role in the long-running debate surrounding the evolution of the earliest land plants.
The fossils at he Yea site are preserved mainly in Limestone. Limestone is a sedimentary rock composed primarily (at least 50%) of calcium carbonate (CaCO3) in the form of the mineral calcite. All limestones contain at least a few precent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite and other minerals. It can also contain large nodules of chert, pyrite or siderite.
It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and faecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water.
Sedimentary rock is important because it often contains fossils and gives clues about what type of rock was on the Earth long ago. Just like a tree's rings tell a lot about its environment, layers found in sedimentary rock can tell about important changes in the environment.
The layers in the rocks here can be seen easily as there are many different colours.
Limestone is formed in two ways. It can be formed with the help of living organisms and by evaporation. Ocean-dwelling organisms such as oysters, clams, mussels and coral use calcium carbonate (CaCO3) found in seawater to create their shells and bones. As these organisms die, their shells and bones are broken down by waves and settle on the ocean floor where they are compacted over millions of years, creating limestone from the sediments and the pressure of the ocean water.
The second way limestone is formed is when water containing particles of calcium carbonate evaporate, leaving behind the sediment deposit. The water pressure compacts the sediment, creating limestone. Because limestone is often formed from shells and bones, it is a light colour like white, tan, or grey. The colour of the limestone depends on the other sediments in the mixture besides the mineral calcite, which is white; impurities such as sand, clay, and organic material are also present in limestone and affect the colour.
There are a few ways to recognize limestone. First of all, it is a soft stone and when it is scratched with a sharp object, it becomes a white powder. When limestone comes in contact with an acid like vinegar or hydrochloric acid (HCl), the stone will actually bubble and deteriorate and then neutralize the acid. This is something you could try at home.
Limestone is important to making cement, but it is also found in other industries such as sugar refining, glass making, and leather tanning. Crushed limestone is often underneath roads and underneath railroad tracks. When limestone is heated, it helps manufacture iron and steel as well as alumina and magnesia. Limestone helps clean drinking water and treat sewage. Farmers will often spread fertilizer that contains ground up limestone on their crops. The limestone in the mixture is a source of plant nutrients and neutralizes soil acidity.
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1. What are the main colours of the rocks at the site?
2. What do these colours suggest?
3. Why does Limestone bubble and deteriorate when it is exposed to acids?
4. A picture or your team or GPS at the site (Optional)
Sources:
http://www.environment.gov.au
https://www.irvmat.com
http://www.hometrainingtools.com
