Testing macroevolutionary patterns in the fossil record
Dr. Matthew Wills, University of Bath
Biologists studying extant organisms have a huge battery of methods at their disposal. Morphology can be observed and dissected in great detail, physiology and biochemistry can be made the subject of experiment, behaviour can be observed, and heritable changes within populations can be studied from generation to generation. Information is available at tremendously high temporal resolution (the ‘ecological’ time scale). But life has a history spanning something in the region of 3.5 billion years, with Metazoa originating at least 540 million years ago. The extant biota is just one time slice of this history. However great our understanding of living animals, we could never have predicted the existence of dinosaurs from looking at today’s birds and reptiles, or giant 5m long sea ‘scorpions’ (eurypterids) from studying spiders and mites. Fossils provide us with less detailed morphological and palaeobiogeographical information, but over vastly longer (geological) time scales.
In the shadows and over the heads of the Isle of Wight dinosaurs
Dr. Steven Sweetman, School of Earth and Environmental Sciences, University of Portsmouth,
The Isle of Wight has the most diverse Early Cretaceous (Barremian) non-avian dinosaur fauna yet recorded and its history of discovery spans some 180 years. In contrast, until recently, remains of the small animals that must surely have lived with the dinosaurs were virtually unknown and the very small number that had been found were poorly preserved. Did this poor preservation and the apparent paucity of small vertebrate remains accurately reflect species diversity, fossil abundance and preservation in the island’s dinosaur-bearing strata? If not, what was to be found and what would these fossils tell us about life on the Isle of Wight 130 million years ago? These were the questions at the heart of an ongoing study commenced in 2002, the results of which have been spectacular. A remarkable microvertebrate assemblage, including small dinosaurs for which there are currently no macro remains, has been recovered. This paints a very different picture from the previously accepted view of the world in which the Isle of Wight’s Barremian mega-fauna lived.
Dr. Peter Allison, Earth Science & Engineering, Imperial College, London
Much of the marine stratigraphic record, and the history of evolution and climate change archived within it,
was deposited in expansive epicontinental seas for which there are no suitably scaled modern-day
analogues (Fig. 1).
Figure 1. Palaeobathymetric reconstruction of the Hettangian Stage (Lower Jurassic) of
the Laurasian Seaway. Palaeogeographic configuration is modified from Dercourt et al.
(2006) and paleodepths are approximately constrained from a detailed literature review.
The tides in these seaways have been variously argued as being either slight as a result
of frictional damping or high as a result of resonant amplification. Tides are important because they influence
sediment architecture and water-body mixing. Numerical models have supported the notion of frictional
damping but outcrop sedimentology has identified the presence of abundant tidally modified sedimentary
rocks in ancient epicontinental sea deposits.
Recent work using the Imperial College Ocean Model (ICOM), a fully hydrodynamic, finite element ocean
model, shows that the majority of ancient epicontinental seas were likely to have been micro-tidal (tidal
range of up to 2 m). Detailed modelling has, however, shown that local amplification and elevated tidal bed
shear stress typically occurs as a result of resonance and paleogeographic funneling in embayments and
over shallow platforms.
Dr. Allison will introduce the model and give an overview of its novelty and utility for a range of broadly scaled
applications. The latter will be illustrated with a series of verification exercises that includes modelling tidal
range, stratification and bed shear stress on the NW European Shelf. Ongoing work is assessing the impact
of amplified currents on seasonal stratification in the Lower Jurassic seaway of NW Europe and provisional
results will be presented. This work has broad applicability to our understanding of sediment dynamics, nutrient cycling and biodiversity in ancient epicontinental seaways.
Virtual Fossils: soft-bodied sensations from the Silurian
Professor Derek Siveter, University of Oxford
The Herefordshire Lagerstätte is a unique fossil deposit of Silurian
age (about 425 million years old) in which the fossils are preserved
in marine-deposited volcanic ash. They are remarkable in that
not only biomineralized shelly forms are preserved, but also
soft-bodied invertebrates, and in spectacular three-dimensional
detail. Soft-bodied faunas from the Silurian are largely unknown, and
the Herefordshire fauna provides us with a previously unavailable
window onto a community from a time some 100 million years after the
Cambrian explosion event. Further, the Herefordshire fossils are
‘released’ from the rock by a novel technique. Digital images of the
specimens are combined by the computer to reconstruct the animal in
minute detail as a ‘virtual fossil’ that can be examined interactively
on screen, and the computer reconstructions of the various specimens
can even be turned into large-scale physical models.
Violent birth of the Earth and the source of precious metals
Dr. Matthias Willbold, University of Bristol
Our solar system was formed about 4.56 billion years ago by the gravitational collapse of a proto-stellar cloud. The first 500 million years of the solar system were a decisive time for the geological evolution of the Earth into the planet we know today and how it became a habitable place. Understanding the chemical and physical processes by which the Sun and the planets were formed is of central interest to Earth and planetary sciences. These processes ultimately delivered water and the essential organic compounds to Earth from which life originated and are, therefore, key to the environmental and biological evolution of our planet.
Current numerical and chemical models suggest that the Earth’s formative years were tough. It grew by colliding with its neighbouring planetary bodies, ultimately emerging the victor having incorporated the opposition. The energies involved in these violent impacts were sufficient to melt much of the entire growing planet, allowing dense iron metal melts to sink to the centre to form the Earth’s core. The release of immense amounts of potential energy by the sinking of the metal melts, together with the internal heating of the Earth by the decay of short-lived radioactive elements may be responsible for the existence of a super-heated liquid outer core. This turbulently spinning liquid outer core is responsible for maintaining a magnetic field around the Earth shielding us, to this day, from the solar wind, a stream of high energy charged particles emanating from the sun. The infant Earth was constantly shattered by catastrophic collisions with other proto-planets that probably re-melted the whole planet several times and must have left the Earth an inhospitable place for life. The accretionary phase culminated in the collision of the proto-Earth with a giant impactor, most likely the size of Mars, less than 100 million years after the start of the Solar system. This massive impact event ejected vast amounts of material from the proto-Earth and flung the impactor into an orbit around our planet. Numerical simulations suggest that, after cooling, this material finally coalesced to form the Moon.
What followed was a much quieter time in the solar system, marked only by the comparatively low-energy impacts of meteors on the young Earth and Moon. During this time, the decline of giant impact events and the progressive cooling of the Earth’s surface may have allowed the formation of an initial planetary crust. Later tectonic processes destroyed all remnants of both, the crust and the meteoritic impact sites on Earth. However, the final traces of this ‘terminal bombardment’ can still be seen today by the cratering of the lunar surface. Yet, it was this terminal bombardment that may prove to have been crucial for the formation of life on Earth. It has been suggested that this late meteoritic shower delivered most of the ingredients essential for life, such as water, carbon and other volatile compounds. This rather ‘mild’ meteoritic bombardment of Earth - also called ‘late veneer’ - terminated about 3.9 billion years ago, shortly before the emergence of first life. However, the energies released during the waning stages of this bombardment, may have sustained widespread hydrothermal activity within the Earth’s crust and may thus prove to be conducive to life’s emergence and early diversification.
The formation of the core also depleted the silicate portion of the Earth in elements that have a high affinity for metal phases, so-called highly-siderophile elements, like precious metals. According to this model, the Earth’s mantle and crust should be devoid of any highly-siderophile elements, which is at odds with the fact that we can still mine them today. I will explore, to what extent the ‘terminal meteorite bombardment’ replenished the precious metal content of the Earth’s mantle during the ‘late veneer’ epoch more than 3.9 billion years ago.
The Monnow Valley - Landscape evolution on the Old Red Sandstone
Dave Green, University of Bristol, Director of Geostudies
Despite flowing from source to mouth entirely in the ORS, this small Welsh Borderland river contains evidence for spectacular landscape evolution, both regionally and locally; and with its tributaries, provides dramatic and well-known scenery derived from a variety of rock types,structures and processes.
The talk precedes a field trip to the Monnow Valley to be led by Dave Green on July 7th
Microbialites (stromatolites), tufa and reservoirs
Professor Maurice Tucker, University of Durham
Microbes have a lot to answer for - in geological terms they produce some spectacular rocks and their deposits are also very important hydrocarbon reservoirs, (recent huge discoveries offshore Brazil). Stromatolites provide evidence of the earliest life on Earth. Tufa, common in the Bath/Cotswolds area, is also produced by microbes (some say!). So should make for an exciting talk.....
Fudge factors in lessons on crystallization, rheology and morphology of basalt lava flows
Dr. Alison Rust, University of Bristol
“A close analogy exists in the making of fudge, wherein if the candy is poured or otherwise agitated after crystallization has advanced beyond a certain stage there results a rough, spinose, somewhat granular surface
akin to the surface of 'a'a” Macdonald (1953)
In many respects, fudge is a good analogue for basaltic lava, and making fudge leads to memorable lessons on both the fundamentals of crystal nucleation and growth and the importance of crystals in controlling the morphology of
basaltic lava flows ('a'a vs. pahoehoe). The talk will discuss the role of crystals in basaltic lava flow rheology and morphology, compare basalt and fudge crystallization processes and textures, and assess the fudge-basalt analogy. An added bonus will be samples of 'a'a and pahoehoe fudge to taste!
Ice sheets and sea level rise: past, present and future.
Professor Jonathan Bamber, Director, Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol
A consensus is beginning to emerge about both the magnitude and trend of mass losses from Antarctica and Greenland over the last ~15 years, covering the contemporary satellite era. Here Prof. Bamber reviews the results of this work, explains the origin of the inconsistencies between estimates and considers the mechanisms responsible for the dramatic changes in ice dynamics observed. He will also provide an overview of sea level rise since the last glacial maximum to place the recent observations in context.
Reliable, direct observations of the contribution of both ice sheets over a longer time scale do not, in general, exist and have been estimated from proxies, which contain large uncertainties. It is difficult, therefore, to assess how representative the recent satellite-based observations are and whether they represent a secular, or short term, acceleration in mass loss. Are we witnessing ice sheet ‘weather’or ‘climate’? Based on glaciological theory, he will speculate on this and on the likely response of the ice sheets to climate forcing over the coming century.
Eight Evolutionary Myths: the closing of the Darwinian mind?
Professor Simon Conway-Morris, Department of Earth Sciences, University of Cambridge
Prof. Conway-Morris’ focus of research concerns the study of the constraints on evolution, and the historical processes that lead to the emergence of complexity, especially with respect to the construction of the major animal bodyplans in the Cambrian explosion. His work is central to palaeobiology, but is also of great interest to biologists and bioastronomers, as well as the wider community.
Prof. Conway-Morris is a Fellow of the Royal Society.