Thursday, February 27, 2014

Pictures of the Moment - Muddy Mats of Algae are a Tourist Attraction in Western Australia

Modern stromatolites living in Hamelin Pool, in the Shark Bay world heritage site, Western Australia. Photo taken April, 2008. These layered mounds of mud and algae are a nirvana for geologists on holiday.

Single-celled organisms, the cyanobacteria of Hamelin Pool are descended from the oldest known forms of photosynthetic life on Earth. A scene like this would have framed the pinnacle of the food chain over three billion years ago.
The American Heritage Science Dictionary defines a stromatolite (strō-māt'l-īt') as a generally dome-shaped structure consisting of alternating laminations of carbonate or silicate sediment and fossilized algal mats. Layered stromatolites are produced over time by the trapping, binding, or precipitating of sediment by groups of microorganisms, primarily cyanobacteria (blue-green algae) growing in shallow-water biofilms. They are distributed throughout the world in the early fossil record and represent some of the oldest recognized forms of life, from over three billion years ago. Similar organic structures continue to form today in restricted hypersaline environments, especially in Western Australia.

Fossilized digital (finger-like) stromatolites from the Biwabik Iron Formation of the Mesabi Iron Range (approximately 2 billion years old), LTV Steel iron mine, Hoyt Lakes, Minnesota. These stromatolites are anchored in an oxidation zone (red jasper), but grew upward into an anaerobic zone (black). Spaces between the stromatolites are filled with round green oncolites, black magnetite crytals and siderite. Thin vertical cracks/fissures are filled with bituminous anthraxolite.
Living stromatolites are rare. The only other known marine location for modern, living stromatolites outside Western Australia is in the Bahamas. Modern stromatolites require hypersaline water, an environment that is inhospitable for their primary predator (a snail). Not far from Hamelin Pool, in the Pilbara region of Western Australia, are fossils of stromatolites over 3.5 billion years old, the earliest easily-recognizable fossils on Earth.

The Hamelin Pool Marine Nature Reserve is located adjacent to the Hamelin Pool Telegraph Station, about 30 kilometers (19 mi) west of the Overlander Roadhouse on the North West Coastal Highway of Western Australia (Wikipedia). Access is via Hamelin Pool Road and then through the telegraph station grounds. There is no charge for access.