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The Geology Section (C) of the Leicester Literary and Philosophical Society presents: GeoDetectives:
Unravelling Earth's mysteries? Annual Saturday Seminar 17 March 2012, 10.30am - 4.30pm Assemble from 10.00am; Reception to follow the Seminar Lecture Theatre 2, Ken Edwards Building, University of Leicester |
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This year we take a step back in time to review how breakthroughs in geoscience were made, while at the same time answering some of the fundamental questions about the geological history of the Earth. The day will start by unravelling the determination of the age of the Earth, followed by that great geological controversy 'plates or plumes'. Later talks will discuss the discovery of enigmatic fossils and our global mineral resources. The day will conclude by evaluating the evidence for the movement of humans or artefacts and finally, what will become of the Earth after us? Our Geodetectives for the day are Professors Jane Evans, Gillian Foulger, Randy Parrish, David Siveter, Dr. Jan Zalasiewicz and Mr Andrew Bloodworth., all highly regarded leaders in their field of research. |
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Tickets for the Seminar and reception are £20.00 with a buffet lunch or £15.00 without lunch. Please purchase tickets by downloading and completing the registration form. For more details about the Seminar, please contact Joanne Norris (j.e.norris@ntlworld.com; 0116 2833127). |
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Seminar Programme |
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10.00 |
Assemble & Coffee |
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| 10.15 |
Opening Mark Evans, Chairman, Geology Section (C), Leicester Literary and Philosophical Society |
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| 10.30 |
100 years of geochronology from Arthur Holmes to the present: how do we know the age of the Earth and Solar System? Professor Randall Parrish (University of Leicester). |
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| 11.15 |
Plates versus Plumes: A Geological Controversy. Professor Gillian Foulger(Durham University). |
12.00 |
Buffet Lunch |
| 13.00 |
The Silurian Herefordshire Lagerstatte: Soft-Bodied Sensations Released From The Rock David Siveter (University of Leicester) |
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| 13.45 |
The secret life of metals: where do they come from and where do they go? Andrew Bloodworth (British Geological Survey) |
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| 14.30 |
Refreshment Break |
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| 15.00 |
Tracing visitors to our shores over the last 5000 years. Professor Jane Evans (Leeds University). |
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| 15.45 |
The Earth after us? Dr Jan Zalasiewicz (University of Leicester). |
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16.30 |
Discussion and Concluding Remarks |
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16.40 |
Reception. To be held in Ken Edwards Building |
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Seminar abstracts |
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Professor Randall Parrish University of Leicester.
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Abstract Arthur Holmes was a very remarkable earth scientist who on several fronts, made seminal scientific contributions that were decades ahead of his time. 100 years ago he published a remarkable paper that presented for the first time chemical measurements of the geological age of minerals that were placed within a stratigraphic context, demonstrating how the earth had to be billions of years old. In 1913 at the age of 23, he wrote a ‘little book’ entitled “The Age of The Earth” wherein he discussed all manner of implications of Earth’s antiquity and radioactive decay. In doing so, he laid the groundwork for a temporally‐graduated geological time scale, for modern views about mantle convection, and for the science of geochronology using radioactive decay. This talk illustrates all of the modern pivotal methods of U‐Pb geochronology that have defined the age of the solar system to 4567 Ma, demonstrated the separation of the Earth from this larger system some tens of millions years later, followed by the consolidation of the core‐mantlecrust land‐ocean‐atmospheric Earth system as we know it. It will reflect on how we have used earliest solar system condensates, chondritic and metallic meteorites, samples returned from the Moon, and the earth’s oldest materials (zircons) to work all of this out, and reflects on both the frontiers of geochronology and the astounding contribution Arthur Holmes made 100 years ago.  |
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Plates versus Plumes: A Geological Controversy. Professor Gillian Foulger Durham University
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Abstract Mantle plumes were originally proposed by Morgan in 1971, who defined precisely their characteristics and predictions. However, subsequent research has been largely unsuccessful in confirming those predictions. Despite this, instead of the theory being abandoned as would have occurred, for example, in medical research if a drug were found to not produce the expected results, the plume model was progressively adapted to encompass unpredicted observations. Plumes have been proposed to come from almost any depth, to rise vertically or tilt, and to flow for thousands of kilometres laterally. They may have narrow or broad conduits, no plume head, one head, or multiple heads. Often, several mutually inconsistent plume models have been proposed for a single “hot spot”, to account for data from different sub-disciplines within the Earth Sciences. Plume theory, as applied today, is so flexible it amounts to an unfalsifiable, data-independent, a priori assumption. In a quest to find models that fit the observations without ad hoc assumptions or appeals to coincidence, the “Plate” model has been developed. This attributes anomalous volcanism to permissive volcanism in areas of extension. The variable volumes of melt produced are attributed primarily to variations in source fertility. A third of all “hot spots” occur at spreading plate boundaries, and many lie in exteding intraplate regions such as the East African Rift. Fertility may be imparted to the mantle by subducted slabs of oceanic lithosphere, and lithsophere delamination. Fertile mantle has a solidus as much as 200˚C lower than that of standard depleted mantle peridotite and thus can produce more melt at the same temperature. This alternative model for the genesis of “hot spots” raises many new questions and challenges, and is ushering in a wealth of novel new research problems previously unconsidered. |
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The Silurian Herefordshire Lagerstatte: Soft-Bodied Sensations Released From The Rock David Siveter University of Leicester
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Abstract Our understanding of the history of life on Earth relies heavily on the fossil record, and especially on rare cases of so-called exceptional preservation (lagerstätten), where soft parts of animals and entire soft-bodied animals are preserved. Such exceptionally preserved fossils provide an unparalleled view of animal palaeobiology and the true nature of animal biodiversity. The lecture will illustrate on-going research on spectacular fossils from 425 million year old Silurian rocks of Herefordshire in the Welsh Borderland. This is a fossil biota of global importance, containing representatives of many major groups of animals. The fossils are being recovered and studied by tomographic techniques, resulting in the reconstruction of high fidelity three-dimensional ‘virtual fossils’ that furnish remarkable anatomical details of the animals. These fossils are crucial in helping to fill a gap in our knowledge of the history of life and to resolve controversies about the relationships and evolution of animals still alive today.
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The secret life of metals: where do they come from and where do they go? Andrew Bloodworth British Geological Survey
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Abstract The digital and environmental technologies which we will rely on to deliver a prosperous, low carbon economy often contain metals which have previously been of little interest to man. Despite the fact that elements such as indium, rhenium, gallium and the rare earths are vital ingredients in a wide range of high technology components such as magnets, batteries, solar cells and display devices, our comprehension of their 'ecology' compared to volume metals such as copper, lead and aluminium is relatively poor. Consumption rates are rising rapidly and there is now an urgent need to better understand the origins and concentration processes of these elements in the Earth's crust. We also need to maximise efficiency of use (do more with less), ensure that we recover and recycle these elements where possible and improve our understanding of what might happen if we lose them into the natural environment. This event will examine the secret life of 'technology metals', from their origins in the Earth, through their extraction, use, re-use and substitution by man, to their ultimate fate in the natural environment. .
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Tracing visitors to our shores over the last 5000 years. Professor Jane Evans Leeds University
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Abstract One of the big questions in archaeology is: Do people move or do artefacts move? If you come across a burial in Britain, of a person who has a beautiful Germanic brooch, can you conclude that the person is of continental origin, or simply that a German brooch was bought in Britain? At the larger scale the questions that are being asked are: was there a large influx of Saxons/Romans/Vikings into Britain who settled here and change the culture, or did a few individual, and their contacts, change the social habits of the indigenous population? Isotope analysis is providing a method of addressing these questions because we can look at the composition of someone’s tooth and determine whether they came from the area in which they are buried, or if they are from elsewhere. This is done though the analysis of strontium and oxygen isotopes in tooth enamel. The strontium isotope composition can be used to relate a person, via geology, to the land on which they lived and derived their food, whereas oxygen isotopes reflect the climate zone in which they were raised. Together, these two “fingerprints” are providing us with new insights into the behaviour and movement of people in the past. The picture that is emerging from studies of Bronze Age people in Britain is that they were very mobile and there is evidence for individuals coming to Britain from continental Europe. The “Amesbury Archer” as he was named, was a 35-40 year old man buried close to Stonehenge in the richest Bronze Age burial on Britain. His grave contained many artefacts of which some were clearly of non British origin. Isotope analysis of his tooth enamel shows that he is very unlikely to have spent his childhood in Britain but is more likely to have come from an area near the Alpine foothills. This talk explains how isotope analysis on tooth enamel is undertaken and illustrates the technique with examples from different historical and prehistorical periods.
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Dr Jan Zalasiewicz University of Leicester
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Abstract The Earth’s history is a 4.6 billion narrative that can be teased out, forensically, by the geologist from myriad clues preserved in the strata of this planet. It is a story of glaciations and global greenhouses, of the rise and destruction of mountain belts, of the evolution of life-forms both enigmatic - as our own local Charnia biota, for instance – and familiar: the ammonites, trilobites, mammoths and so on. But what position can the brief history of humans have within this almost unimaginably long narrative? This talk will consider the evidence, and the story, that might emerge as alien visitors explore the Earth, one hundred million years in the future. These far future alien visitors will find no obvious traces, ruined cities, say, or skeletons in caves. They will have to consider the world of the underground - and become Terran geologists (and, more particularly, stratigraphers). Their journey to discover the Earth’s lost civilization will be lengthy and tortuous, with many geological puzzles – quite as long and involved as our own geological enquiries into the dinosaurs, and into what might have killed them off. What might they find first? A long history of the almost immeasurably long life and eventful times of this planet, preserved in the strata. This geological archive is a by-product of plate tectonics: it is unparalleled in this Solar System, and probably rare in star systems generally. They will find trilobites, and ammonites, and dinosaurs too – and fossils of whatever animals and plants will follow the brief, geologically infinitesimal human reign. They will find evidence (just as we do today), in the strata, of times of an abundant, diverse and stable biology, stable over long time-scales. They will also find times of environmental upheaval, of climate change, of changes to sea level and to ocean chemistry, of sudden reductions in biological diversity. In one of these episodes of global change, there will be other geological signals, not seen in other of the past global perturbations. Geochemical anomalies, of metals, nitrogen, phosphorus. Enigmatic fossils. Signs of worldwide biological invasions. This will strike them as strange – just as we today, find the phenomena associated with the Permo-Triassic and Cretaceous-Tertiary boundaries puzzling, and fascinating. Following these clues – often buried far underground, and only rarely at the surface – our future explorers will then, finally, stumble upon a petrified city, perhaps with human remains. And only then, can they begin to try to understand our long-vanished civilization. |