370 million years ago
Late Devonian
Early Carboniferous
359 million years ago
Early Carboniferous
350 million years ago
Middle Carboniferous
350 million years ago
Late Carboniferous
315 million years ago
Changes in sea level over time, from 370 million to 315 million years ago. Ireland was part of a larger continental mass, and following the Late Carboniferous the land was raised and subjected to mountain building pressure from the south east. In the Late Carboniferous deep basins, indicated by deeper blue, formed. well have been that they simply thinned out or became sandy towards Loop Head. The shales do crop up on the other side of the estuary, north of Ballybunnion, but no one could be sure that they actually continued under the Shannon. Drilling eliminated a lot of the guesswork. So far five drills have been made, varying in depth from 100 to 235 metres and as Dr Haughton commented, it all takes a lot of time because the rocks are so hard. At Loop Head, where drilling went down to 235 metres deep the aim was to get through the overlying Ross Sandstone to the shales that should, according to projections, have lain below. Choosing where to drill, said Dr Haughton, involves a certain amount of risk. The unseen underlying layers might not be horizontal, so a vertical drill, if it has to penetrate rocks at an angle, might never hit the lower levels. However, all went well, and last year the drilling team came up with results from Loop Head that indicated how the same Clare shales that are seen exposed further back in the cliffs, continue out and down into the basin. “We now know that the succession extends across the River Shannon and occurs beneath the level of the exposures at Loop Head,” Dr Haughton explained. Overall, the picture that emerges is of a shallowing up from an oxygen starved basin floor with sediments coming in from the south west and gradually fanning out to the north east. “What we are looking at,” said Dr Haughton, “is a scale of about ten kilometres,” and that, he adds, is about right for the size of an oil field. Similar deposits, he said, are targets for active exploration in the Gulf of Mexico and elsewhere. Dr Haughton is keen to emphasise that there are very few places where such features can be examined in such detail, and as he remarked, there is a lot more to be discovered. As he commented, this is not just something of local interest. Geologists from all around the world want to be involved in this research, and making them welcome would boost both to the community and to the standing of Irish geoscience. “Our dream,” he said, “is to have a science centre somewhere on Loop Head,” where geologists and students from around the world could come to study an ancient basin system.
Maps and charts based on the NEED project material.
IT WAS thought that land plants evolved from green fresh water algae belonging to the Charales group, but genetic analysis points to an origin in a less complex group of Zygnamatales algae. In the open access journal, EMC Biology, an international group of researchers has reported that the more advanced form of reproduction shown in the Charales group, with a big egg and small sperm, led scientists to assume that these algae would have given rise to land plants about 500 million years ago. However, as they discovered, the Zygnamatales algae were more closely related to land plants, yet they relied on a more primative method of reproduction, involving fusion of similar sized cells. As one of the researchers, Dr Becker, explained, it appears that the Zygnamatales, having raced ahead in evolutionary terms, then had to retreat, possibly due to the onset of adverse conditions such as the lack of water. Although they discarded some of their complexity in order to survive, genetic traces remained to show that they a number of traits in common with land plants, among them, the production of eggs and sperm.
Ancestral plants
Conjenction in Spirogyra algae, image, John Alan Elson
Wild flowers
AfTeR spending more than 30 years tramping around the countryside with her camera, Zöe Devlin has put together an impressive collection on wild floswers. Her interest was sparked off by an elderly aunt who, having taken her up a hillside in Glenmalure took out a magnifying glass to reveal the flower of an orchid in all its detail. As Zöe remarked, from that day onwards, she was hooked. eventually her own daughter suggested that it would be a good idea to set up a webside for all those images. The result, for all to see, is at www. wildflowersofireland for anybody interested in knowing what they are looking at when out and about, this is a great site, packed with photographs that make it easy to identify Ireland’s wild flowers. There is also a very useful guide to show what’s in flower now. Zöe’s book on the wildflowers of Ireland is due out this Autumn from the Collins Press in Cork.
SCIENCE SPIN Issue 48 Page 25