Pollen Thermometers

20 December 2001

Every hay fever season stop and think about how useful those irritating little pollen grains can be. Not only are they essential to develop a new plant, but scientists at Geoscience Australia can use them, or at least their ancient ancestors, to help discover new oil deposits many 100's of metres below the earth's surface.

Pollen grains and spores are resistant little things. Their outer skin is like a plastic bag and very hard to break down and so they can be found as fossils imbedded in rocks 100's of millions of years old. Because of their size -- most require a microscope to be seen -- even the smallest samples of rock can contain many pollen fossils.

Because it is made of carbon, the outer casing of a fossil pollen or spore grain acts as a thermometer. As they heat up they change colour becoming darker and darker as the temperature increases. It's really like toasting a slice of white bread -- too hot and it turns black! However, once they change colour, they don't revert back to their original hue when the rock cools down. By measuring their final colour, scientists can discover the maximum temperature that the fossil pollen, and therefore the surrounding rock, has been over many millions of years.

Knowing this temperature is critical for the formation of oil in rocks containing the right organic matter. Not enough heat will mean that the organic matter will not convert to oil. Too much heat will convert the oil to gas or even destroy the organic compounds completely. It's getting the heat just right for oil formation that is so critical.

It is funny to think that the very pollen grains which may lead to discovering a new oil field may have made a dinosaur sneeze some 100 millions years ago!

One of the roles of Geoscience Australia is to undertake research into all the possible rock formations that could potentially contain oil in our country. In doing so, exploration companies are encouraged to come and explore for oil reserves, keeping us self reliant on our own reserves as well as creating wealth for the nation.

Topic contact: media@ga.gov.au Last updated: October 4, 2013