Before people go out to buy a geological hammer to test the rocks for casts and impressions during wadi-bashing trips, note that these remains are actually molecular, that is, invisible to the naked eye. They've been found in a bio-marker horizon in shallow sedimentary rocks, presumably as a result of bio-geochemical analysis, in sub-surface rocks in the South Oman Salt Basin (pers. comm. Dr Gordon Love). Dr Love points out that "rocks in north Oman are too mature for detailed biomarker work."
The remains are not bones, since animals with either outer or inner skeletons did not exist at the time. The marker molecules in this case are of 24-isopropylcholestane, a breakdown product from lipid molecules which exist in the cell walls of sponges. The results of the analysis are consistent with the theory that the original animals were tiny sponges (demosponges), which lived then and continue to live in shallow marine environments.
Since there wasn't anything like as much oxygen in the water as there is today, the size of the animals remained very small.
What's significant is that palaeoclimatologists now have more evidence on which to revise their ideas about what was happening to the Earth's climate all that long time ago.
Evidence of an extremely severe glaciation has long been recognised at the boundary between the Cambrian and Precambrian. You can find rocks that appear to be tillites (glacial deposits) in Oman, and in other countries on tectonic plates which would have been in tropical regions at the time.
The extent of the glaciation gave rise to a theory 50 years ago, that the whole world had been effectively frozen up, perhaps to a depth of 2 km in the oceans. This theory was named 'Snowball Earth' in the 1980s.
Scottish geologists refuted this claim in 2002 when they discovered evidence of sediments which had been deposited in water, from that era.
Well now, the inferred remains of these little sponges in Omani rocks, which predate the end of the Marinoan glaciation of the Cryogenian Period [about 850 to 635 million years ago], also show that the seas were not frozen over, since life, of a sort, was able to be sustained. What's more, the fact that it was possible to detect the 24-isopropylcholestane at all indicates that the biomass was substantial.
Peridotites, carbon dioxide absorption and a solution to global warming?
I didn't mention another geological story last November, after it appeared in the press. In the chattier news sources, headlines like, 'Oman's rocks rescue world from global warming!' would not have gone amiss.
To be honest, I was hoping to find a more sobre source of academic information which would verify the stories. Now I have.
Oman has the largest exposed mass of peridotite in the world, in the mountains of Al Hajar. Peridotite is the stuff of the Earth's mantle. The Samail ophiolite was heaved upwards to the Earth's surface by massive Earth movements some 90 million years ago.
Because peridotite formed in conditions of high heat and pressure deep in the Earth, its mineral composition is unstable at the Earth's surface. Its minerals, primarily olivine and pyroxene, are therefore highly susceptible to chemical reaction and alteration. The new minerals that form are predominantly serpentine, a hydrous silicate, and magnesite and calcite, carbonates of magnesium and calcium respectively.
The serpentine forms by the reaction of the peridotite with water and the carbonates form by the reaction of the peridotite with atmospheric carbon dioxide.
Two geologists from the Lamont-Doherty Earth Observatory at Colombia University in New York, decided to investigate the rate at which the Oman peridotites transformed into these minerals. They were particularly interested in the rate of carbonation - how long it takes for the peridotite to be transformed into carbonates.
Much to their surprise, they discovered that the rate of carbonation is very fast in geological terms. The visible extent of conversion to carbonate has taken only 26000 years.
Since the volume of the Oman ophiolite is so huge, they estimated that it could absorb 100,000 tons of carbon dioxide each year.
Their paper suggests that a field test of two boreholes linked by a shaft at the bottom of the holes could be drilled off shore into the peridotite. Hot fluid would be pumped into one of the boreholes initially and then injected first with pure carbon dioxide and then with seawater which contains carbon dioxide. Subsequently, the temperature gradient across the boreholes and the exothermic (heat emitting) conversion of the peridotite to carbonates would generate enough heat to sustain the movement of the water to the surface. The process would be self-generating.
Although the use of seawater is inefficient, it does avoid the expense and engineering of capturing carbon dioxide directly from the atmosphere and of transporting it to a storage area.
Of course, the idea has to be tested. There would be an impact. The peridotite would be broken up and weakened. The process would cause micro-earthquakes as a result of this fracturing, virtually undetectable on the Earth's surface, claim the geologists. And there would be an impact on local water supplies drawn from the peridotite. Sea water is salty.
But it's nice to read of some genuine research with practical implications.
Peter B. Kelemen and Jurg Matter, 2008, In situ carbonation of peridotite for CO2 storage, Proceedings of the National Academy of Sciences of the USA, 105 (45) pp 17295–17300 Summary