What is a Stromatolite?
Stromatolites are layered bio-chemical accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms (microbial mats) of microorganisms, especially cyanobacteria. Fossilized stromatolites provide ancient records of life on Earth by these remains, some of which may date from 3.7 billion years ago. Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens.
Stromatolites are a major constituent of the fossil record of the first forms of life on earth. The earliest fossils date to 3.7 billion years ago. They peaked about 1.25 billion years ago and subsequently declined in abundance and diversity, so that by the start of the Cambrian they had fallen to 20% of their peak. The most widely supported explanation is that stromatolite builders fell victim to grazing creatures (the Cambrian substrate revolution); this theory implies that sufficiently complex organisms were common over 1 billion years ago.
Why are they important?
Stromatolites created the atmosphere, over great time with great numbers their actions allowed the evolution of more complex creatures, and eventually us.
Modern stromatolites are mostly found in hypersaline lakes and marine lagoons where extreme conditions due to high saline levels prevent animal grazing. One such location is Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia where excellent specimens are observed today
Important Information
This Earthcache starts at the Trezona campground carpark and information board. This is where you can park and where the formed track starts. The track is on the Haywards Huts network and is called “The Trezona Circuit”. The track is well formed and maintained. Water is essential and the track will require a moderate level of fitness. It is just less than 2km to the EC site. There can be snakes in the warmer months, so be aware. The track follows the river bed (under trees) for the first half and crosses former pastoral areas for the second half. If it is sunny, use sun block, take a hat etc.
There is no mobile phone coverage. Let people know what you are doing and your anticipated duration. You will need a dedicated GPSR or printed map to complete the EC.
I half assumed that you will start at the Trezona campground carpark and follow the track and I have noted waypoints of interest and directional relevance.
EC Marker - Track start, carpark and information stand
WP 01 - At this point the track crosses the river bed (dry) the sign is visible across the river
WP 02 - You have come to a junction in the track. Turn right here.
WP 03 - EC site 01
WP 04 - EC site 02
You will pass what is known as “the Golden Spike” – Take time to look for this on the early stage of the track and appreciate its importance to, well, everything. The link below can explain this in more detail.
http://www.pir.sa.gov.au/__data/assets/pdf_file/0012/11055/mj37_ediacara_golden_spike.pdf
The questions relate to the small section between WP03 and WP04 (about 25m).
Question 01
- What are the sizes (Diameters) of the Stromatolites you can see here?
- How many can you see?
Question 02 At WP04 there are some exposed sections of rock:
- Are the layers thick or thin?
- Are they level or wavey?
- Are they above or below the Stromatolites? What does this mean to you?
Feel free to log your find and email me the answers as soon as you can. Photos are encouraged, but please do not post any spoilers.