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Promoting Zambia’s unique fossil forest

IMAGES of coniferous trees that have turned into rock in the Chirundu Fossil Forest.

NKOLE NKOLE, Chirundu
AS WE ascend the hilly area of Chirundu called the Chirundu Fossil Forest national monument, a few goats can be heard bleating not too far from the spot where we are taking pictures and gazing.
The goats wander aimlessly, nibbling at grass here and there and oblivious of the random visitors that are having a tour of the hills which represent their home.
The Chirundu Fossil Forest is considered a unique area by the National Heritage and Conservation Commission (NHCC) and is one site singled out by the Commission to be considered for nomination as a World Heritage Site.
Kagosi Mwamulowe is NHCC regional director in charge of the East-Central region, which comprises Lusaka, Eastern and Central provinces. He also happens to be impressively versed in the history of the Chirundu Fossil Forest.
There are two major categories of heritage sites according to Mr Mwamulowe.
“Natural heritage sites are unique sites which are naturally occurring while cultural heritage sites are those which represent the creative genius of people,” he says.
The Chirundu Fossil Forest happens to be a natural heritage site that was declared a national monument in the 1960s for its unique rock formation.
There is a reason the rock formation here is described as unique.
“These rocks are basically a type of formation that were at one point trees and these trees with time, fell, were buried and fossilised or turned into fossils,” explains Mr Mwamulowe.
One may wonder exactly how this is possible and what may have happened for this phenomenon to come about.
Thankfully, Mr Mwamulowe is a paleontologist whose area of expertise is the study of fossils to determine organisms’ evolution and interactions with each other and their environments. Scientifically, this field is called paleontology and is a distinctive one which Mr Mwamulowe is privileged to be specialised in.
According to him, there could have been a huge flood which forced the trees in the Chirundu Fossil Forest that are conifer-like in nature, to fall. These trees are also synonymous with temperate regions.
Because of the kind of climate Lusaka experiences which is typically semi-tropical or savannah, it is not possible for coniferous trees to thrive in Chirundu.
“As you go up north where you have a high rainfall belt like on the Copperbelt, you find conifers there. If you go to Mbala as well, you will find that there too, conifers are growing,” he says.
In the same way, the type of ecology that existed in the Chirundu Fossil Forest area 150 million years ago was the temperate type which favoured the growth of conifer trees.
With time, the environment around the Chirundu Fossil Forest changed and evidence of this change was seen in the fossils themselves.
“What happened is that there was a huge flood which forced these trees which were growing at that time to fall because of the flood,” Mr Mwamulowe says.
The fossilised trees are in fact quite gigantic. Some of them measure up to half a metre in basal diameter.
As the trees fell, there was also a process of soil erosion and deposition which eventually buried them in the soil.
In the process, because of the rapid deposition of soil, these trees, together with their cellulous material were buried and preserved as such.
There was no combustion to burn the cellulous material. The cellulous materials, in lay man’s terms, are cell materials in a tree.
With time, the carbon material in the cells was being replaced with the material from the surrounding rock or soil.
Silica, the most common constituent in sand was being absorbed by the tree material, replacing all the carbon material which ordinarily should have decayed.
There was then a chemical reaction between the silica compound and the carbon material in the dead trees which produced silica oxide.
The silica replaced the biodegradable material or the carbon material in the rock and in the process, that replacement produced hardened material which is the silica itself as it appears in sand.
Most interestingly, the silica which replaced the carbon material in the rock took the original form of the cells of trees, and hence has a preservation similar to that of a tree.
“In a normal tree, you have those annual growth rings. Those are seasonal growth rings. In each season you have a layer which develops around a tree bark. One layer represents a season, such that if you want to estimate the age of a tree, you can easily count the number of growth rings,” Mr Mwamulowe explains.
As a tree grows, it develops layers which are represented by growth rings that are used in dating trees.
What is exciting about the Chirundu Fossil Forest is that apart from the massive size of the trees, the actual rock formation, there is sandstone which was formed during the Karoo period, which refers to an ice age from 360–260 million years ago.
It is named after the tillite (Dwyka Group) found in the Karoo region of South Africa (and adjacent areas), where evidence for this ice age was first clearly identified in the 19th century.
In terms of dating, the estimation of the age of the fossils in Chirundu is 150 million years.
“These rocks are known as Karoo rocks simply because they resemble the rocks of the Karoo Basin in South Africa and they were formed at the same time and they are mainly found in the valleys of Zambia,” Mr Mwamulowe shares.
You can find the same rocks in the valleys of Gwembe, Luano, North Luangwa and Zambezi.
It is the unique rock formation that compelled the Commission in the 1960s to declare the site a national heritage site through the Heritage Act.
“Our Act mandates the Commission to conserve or protect sites which have unique formation or existence, be it naturally or tampered by man,” Mr Mwamulowe says.
Due to the nature of the fossils found in Chirundu Fossil Forest, Zambia, as State Party to the 1972 World Heritage Convention, was compelled to include the Fossil Forest as one of the national heritage sites it intends to consider for nomination as a World Heritage Site.
A Tentative List is an inventory of those properties which each State Party intends to consider for nomination while a World Heritage Site is a landmark which has officially been recognised by the United Nations (UN), specifically UNESCO.
For it to qualify as a World Heritage Site, Chirundu Fossil Forest has to fall in the same class bracket as other sites in different parts of the world, including the Mosi oa Tunya/Victoria Falls, considered a World Heritage Site because of its exceptional natural beauty.
“When it comes to the Chirundu Fossil Forest we want to demonstrate that it is also a unique site,” Mr Mwamulowe stresses. “But to demonstrate that aspect is not an easy assignment. We have to really do intensive research to prove to the world that what we have here is worth nominating as world heritage material.”
In total, there are seven sites on the tentative list of World Heritage Sites in Zambia. Others include the Dag Hammarskjoeld Memorial Crash site (1997), the Kalambo Falls archaeological site (prehistoric settlement site) (1997), Mwela Rock Paintings (2009), Kalambo Falls (2009), Zambezi Source (2009) and The Barotse Cultural Landscape (2009).
Mr Mwamulowe is a contributor to the 2015 Zambia National Commission for UNESCO Annual Report where he wrote an article on nominating World Heritage Sites and argued the case for Zambia.
Through the relentless dedication of the NHCC and devoted heritage experts such as Mr Mwamulowe, Zambia can hopefully, in the near future, have yet another heritage site listed as World Heritage Property to rival the Victoria Falls which is presently the solely listed World Heritage Site.


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