BATH GEOLOGICAL SOCIETY
LECTURE MEETINGS 2018


Lecture Meetings at Bath Royal Literary and Scientific Institution,
16 Queen Square, Bath at 7.30 p.m.


February March April May June July September October November December AGM 2018

February 8th

Annual General Meeting, 2018

AGM will start at 7.00 p.m. followed by the lecture at 7.30p.m. Please note that the AGM is for members only. Visitors are welcome to attend the evening's lecture.

Bird watching in the fourth dimension: how the fossil record reveals the origin of flight, feathers, and birds themselves

Dr. Daniel Field, University of Bath

Birds are the most diverse and widely distributed groups of tetrapod animals. They inhabit a myriad of different environments, and exhibit incredible disparity in their forms and lifestyles. Unravelling how, when, and why modern bird diversity has arisen demands an appeal to the fossil record of modern birds, as fossils provide us with the only direct evidence of the history of life on Earth. Additionally, understanding the origins of the features that make birds unique - such as feather-assisted flight - forces us to look beyond the fossil record of modern birds themselves. For these answers, we must turn to the Mesozoic record, more than 66 million years ago, to study the early antecedents of modern birds: non-avian dinosaurs.

I will discuss my research related to modern birds and their dinosaurian relatives, covering questions like "how did the ancestors of modern birds survive the end-Cretaceous mass extinction?"; "how have the geographic distributions of modern bird groups changed over the last 66 million years?"; and "how and when did modern avian flight arise?".


Return to Top

March 1st

Finding new uses for old pollen: reconstructing past climate and vegetation change using pollen chemistry

Dr Philip Jardine, University of Münster

Due to their widespread and abundant fossil record, pollen and spores have become a mainstay of research into past vegetation change and floral evolution, and are widely used to infer past climates and date sedimentary sequences. However, palynology as a discipline has remained largely unchanged in its approach for the last 100 years. In this talk I’ll describe how a whole new field of research is opening up, based on using the chemical signature of pollen and spores to extract previously inaccessible information on past climate and vegetation change.

One key insight has been that pollen and spores contain a direct chemical record of past ultraviolet irradiance via concentrations of ‘sunscreen’ compounds, offering the potential to quantify the role of solar irradiance in climate change, identify episodes of past ozone collapse, and determine the timing and rate of mountain uplift. Another has been the discovery of a taxonomic signature in pollen and spore chemistry, greatly increasing the amount of information on plant composition and diversity that can be recovered from palynological samples. I’ll talk about recent developments in both of these areas, and offer some thoughts on the future direction of chemical palynology.


Return to Top

April 5th

"Why Giraffes have such short necks"

Dr. Michael Taylor, University of Bristol

The necks of sauropod dinosaurs were by far the longest of any animals, exceeding 15m.  Four clades with very different cervical morphologies (mamenchisaurids, diplodocids, brachiosaurids, and titanosaurians) evolved ten-meter necks.  By contrast, the neck of the giraffe, the longest of any extant animal, reaches only 2.4m.  Those of theropods and pterosaurs attained at most 3m (Even among aquatic animals, the record is only 7m for elasmosaurs).

Four factors contributed to sauropod neck length: the sheer size of the animals, their distinctive vertebral architecture, air-sacs, and heads that merely gathered food without processing it.  Cervical vertebral innovations included: extreme pneumatisation, which lightened the neck and increased bending resistance; elongate cervical ribs, which allowed hypaxial muscles to shift posteriorly; and, in several clades, bifid neural spines, which aided stability by shifting epaxial tension elements laterally.  Bifid cervical neural spines evolved at least four times among sauropods and were never secondarily lost; they are otherwise found only in Rhea.

However, other aspects of sauropod cervical anatomy remain puzzling: low neural spines reduced the moment arm of epaxial tension members; ventrally displaced cervical ribs increased bulk; and epipophyses were not posteriorly elongated.  These apparent flaws suggest our understanding of sauropod neck mechanics remains incomplete.


Return to Top

May 3rd

'Unlocking the Archive': Antarctic Peninsula Glacial change

Dr Lucy Clarke, University of Gloucestershire

The Antarctic Peninsula is a mountain glacier system comprised of over 400 glaciers, and is an important contributor to historical and future sea level rise. Assessment and monitoring of Antarctic Peninsula glaciers is crucial for understanding sensitivity to climate change. Changes to glacier fronts and ice shelves and glacier acceleration are well documented, but there are almost no data on mass changes on the Antarctic Peninsula. Satellite data have been used to calculate change over the last 3 decades, but methods to quantify this over longer timescales have eluded researchers. However, there is an archive of aerial photography dating back to the 1940s, this has been largely ignored due to the range of technical problems associated with deriving quantitative data from historic imagery and the lack of ground control data. This talk will introduce some of the early expeditions that collected aerial photography of the Antarctic Peninsula and then demonstrate how advances in image processing and capture of modern aerial photography has allowed this archive to be ’unlocked’. The spatial and temporal changes that have occurred on the glaciers over the period of record will then be explored.


Return to Top

June 7th

Subduction zone earthquakes and tsunami – exploring the Sumatra subduction zone (the source of the 2004 Indian Ocean tsunami) using marine geology and geophysics and ocean drilling

Lisa McNeill - Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton

The 2004 magnitude 9.1 earthquake and resulting tsunami originated on the subduction zone margin offshore North Sumatra (part of the Sunda subduction zone system). The resulting tsunami killed more than 200,000 people, devastating large coastal regions around the Indian Ocean, in particular in North Sumatra (Aceh) and Thailand.

Since the earthquake, a large number of countries, in collaboration with Indonesia, have invested in collection of geological and geophysical data in order to better understand the structure of this subduction zone and its potential for large earthquakes and tsunami. The data are also important for a general understanding of these processes and of other subduction zones worldwide. The UK has played a significant role in this effort. This talk will show some of the results of data collected in projects over the last few years, including those led by UK scientists. This includes marine geophysical data that images below the seafloor to show the structure of the subduction zone and the properties of the faults that move and generate the earthquakes. Sediment cores sampling the upper few metres below the seafloor have also been collected to see where submarine sediment flows were triggered by the earthquake shaking in 2004 and in previous earthquakes.

Finally, in 2016, an expedition of the international Integrated Ocean Discovery Program (IODP: scientific ocean drilling) drilled the sediments coming into the subduction zone. These sediments, which originate from the Himalaya and Tibetan Plateau, form the tectonic plate boundary fault – their properties ultimately control the behaviour of the fault. Drilling and sampling of these sediments has now provided information about the properties of the fault zone and why it generated such a large earthquake and tsunami.


Return to Top

July 5th

Dangerous Earth - or why we should be afraid

Dr Simon Wakefield, Cardiff University

Natural hazards such as earthquakes, volcanic eruptions, floods, droughts, wildfires, landslides, storms and tsunamis have happened throughout geological time. The difference now is that as the population of the world increases some people are living in areas that maybe are not particularly sensible from a hazard perspective, but they have little choice. For others, the complexity of modern society means that a major event such as Hurricane Harvey can inflict catastrophic economic and social consequences on even the most sophisticated cities in the western world. This talk will examine the causes of consequences of a variety of hazards and show how, looking ahead, the impact of some  such events is likely to increase as climate, population and land use combine to amplify what are in reality entirely natural phenomena.


Return to Top

September 6th

The Geology of the Earth’s Oceans Past and Present

Dave Green, Geostudies: A JOINTLY ORGANISED BRLSI-BGS TALK

The talk will examine the current state of understanding of the geological processes operating in the oceans and their effects. Our knowledge and interpretation has changed quite radically since the 1950s, and continues to develop, enabling better understanding of the geology of ophiolites, such as the Lizard and Ballantrae; the environmental relationships between plate tectonic processes, the oceans and the mantle, and our interpretation of the geology of our near neighbour planets. Changes that are thought to have taken place in the oceans through geological time will be discussed as well as the anthropogenic effects of the present.


Return to Top

October 4th

Creating the critical zone: dissolving, fracturing, and eating rocks

Dr Heather L. Buss - Senior Lecturer in Biogeochemical Weathering - School of Earth Sciences, University of Bristol

The critical zone is the region of terrestrial Earth extending from the treetops to where rock begins to weather. It's critical because it provides many essentials that we need to survive on this planet - energy, nutrients, food, groundwater; it also mediates the release of toxins to the biosphere, controls water runoff and infiltration, affects the concentrations of greenhouse gases in the atmosphere, and generates dust and sediments. The creation of the critical zone from solid rock is a complex but fascinating set of interlinked processes of chemical reactions, physical transport, fracturing, and metabolism.

The feedbacks amongst these very different processes determine many of the characteristics of the critical zone, such as the shape of it, the depth of it, how fast it evolves, and the fertility of it. Because the critical zone is so critical, it's essential that we are able to preserve (or restore) its functions in the face of global and local environmental change. To do that, we need to understand exactly how these feedbacks work so that we can make accurate predictions of the consequences of environmental change as well as of our interventions. In this talk, I will discuss how these different processes are interlinked with a case study of spheroidal weathering in a tropical granitic rock, with extension to other lithologies and climate zones globally.


Return to Top

November 1st

New fossil discoveries from France and Morocco shed light on the origin of starfish and brittle stars in the Great Ordovician Biodiversification Event

Dr Aaron W. Hunter - Department of Earth Sciences - University of Cambridge

Asterozoans including starfish (asteroids) and their close relatives the brittle stars (ophiuroids) are amongst the most instantly recognisable and iconic marine animals. They are a dominant and successful group of living echinoderms based on their diversity, abundance, and biogeographic distribution. Despite their ecological success and a fossil record spanning more than 480 million years, the early evolution of asterozoans and their echinoderm cousins more generally, remains a mystery. In-fact, they seem to appear suddenly in the early Ordovician with no apparent ancestor in the Cambrian. New discoveries from France and Morocco have begun to resolve this mystery.

Exceptionally preserved fossils, combined with an understanding of the developmental biology have allowed us to reconstruct the sequence of evolution of the asterozoans (with a comprehensive phylogenetic framework). We explore the earliest common ancestors the somasteroids and their Cambrian echinoderm relatives, including a fossil, which is the earliest starfish like animal so far recorded in the fossil record. We then follow these exceptional fossils through the Ordovician as true ophiuroids and asteroids appear and show how they rapidly diversified during the biotic revolution we call the Great Ordovician Biodiversification Event. We demonstrate that these animals survived until the Permian, with some of their descendants still found in the oceans today.


Return to Top

December 6th

Diamond Eruptions

T.M. GERNON - Ocean & Earth Science, University of Southampton, SO14 3ZH

Kimberlite volcanism typically involves the formation of diverging pipes or diatremes (see image below), which are the locus of high-intensity explosive eruptions. The talk will first provide an overview of diatreme formation. I will then focus on a conspicuous and previously enigmatic feature of diatreme fills known as ‘pelletal lapilli’ — well-rounded clasts that consist of an inner ‘seed’ particle with a complex rim, thought to represent quenched juvenile melt. Such clasts are widely documented in a range of pyroclastic successions on Earth, yet are not fully understood. New observations of pelletal lapilli in kimberlites show they coincide with a transition from magmatic to pyroclastic behaviour, thus offering fundamental insights into eruption dynamics and constraints on vent conditions.

We provide strong evidence that pelletal lapilli form by fluidized spray granulation — a coating process used widely in industrial applications, including the chocolate industry. We propose that pelletal lapilli are formed when fluid volatile-rich melts (akin to molten chocolate) intrude into earlier volcaniclastic infill close to the diatreme root zone. Intensive degassing produces a gas jet in which locally-scavenged particles are simultaneously fluidized and coated by a spray of low-viscosity melt. Most fine particles are either agglomerated to pelletal coatings or elutriated by powerful gas flows. The origin of pelletal lapilli is important for understanding how magmatic pyroclasts are transported to the surface during explosive eruptions, where they can be asociated with high diamond grades. A similar origin may apply to pelletal lapilli in a range of alkaline volcanic rocks.


Schematic showing the formation of pelletal lapilli in kimberlite diatremes (Venetia and Letseng, southern Africa).
Return to Top

February

Annual General Meeting, 2017


~END~