Microbial mats (or biomats) are aggregates of microorganisms composed mainly of bacteria and algae. They can grow in a number of environments: shallow seas, lakes, ponds, rivers—and on soils. Because soils form only on land, however, the presence of these microorganisms intermixed with soil means that life must have emerged from the sea onto the land at least 3.2 billion years ago.
When microbial mats develop on soil, they often lead to the formation of laterites, which are soil layers enriched in iron oxides. These layers form when living things decay. The resultant organic acids leach iron from upper layers of soil and deposit them as oxides in the soil layers below. This process creates three distinct bands of soil—an iron-rich layer sandwiched between two iron-deficient layers.
Microbial mats on soil provide direct evidence for the presence of land-based life, but only indirect evidence of an atmosphere rich enough in oxygen to produce a protective ozone layer. Some researchers suggest that microbial mats may be able to develop on land without an ozone shield.
But the combination of iron-rich minerals and fossilized microbial mats in rocks dated at 3.2 billion years old proves both that oxygen must have been present in the Earth’s atmosphere and that life must have been present on land at that time.
To log this EarthCache you have to answer the following questions and e-mail the answers to me:
1. Take a look at the rock speciman near the information panel. How long is it?
2. Give a short description about possible biomats you see.
3. Give an example of ancient life forms producing oxygen according to the panel.
Uploading photos to the cache page is the best way to say thank you to the cache developer and to encourage others to visit the location but is only optional.
NOTES:
- There are no other facilities along the trail except for very nice picnic spots.
- The distance is about 40km from Barberton on a narrow and winding road up to the Bulembu border post to Swaziland with no or limited cellphone reception.
- You can email me your answers in either Afrikaans or English.
Note that a handy guidebook specially compiled for this route is on offer at Barberton Tourism in town.
Enquiries: 013-712 2880 or www.barberton.co.za
Guided tours by Tony Ferrar on 072-376-2581 and Dave Mourant on 082-923-5366.
Thank you to the Barberton Chamber of Business and all those involved to develop this geotrail.
