Scientific Webinars

The evolution of the Patagonian Ice Sheet from 35 ka to the Present Day (PATICE)

Dr Bethan Davies – Royal Holloway University of London

The Patagonian Ice Sheet was an ice sheet characterised by a wide variety of environments, including glaciolacustrine, land-terminating lowland lobes, high mountain glaciers and glaciomarine environments. It dammed large lakes that grew as it receded, which were an important control on ice dynamics. Here we present an overview of the variety of sediment-landform assemblages produced, and use these together with 1669 published ages to reconstruct Patagonian Ice Sheet evolution over the last 35,000 years, from the Last Glacial Maximum to the present day. We use these datasets to untangle the climatic and ice dynamical controls on ice recession, and find that current recession, driven by a persistent negative phase of the Southern Annular Mode, is exceptional within the Holocene.

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What triggered the Cambrian Explosion?

Professor Rachel Wood – University of Edinburgh

The Cambrian Explosion marks the rise of diverse animal groups ca. 540 million years ago, but the triggers for this revolution remain poorly understood. The roots of the Cambrian Explosion are in to be found in the preceding Ediacaran, and we can now document a series of pulses of enhanced seawater oxygen stability over the Ediacaran to Cambrian interval. These coincide with pulses of diversification and increased body size in animals, and the biological control of carbonate production was driven by the rise of predation.

Advent of the Anthropocene Epoch ~1950 CE: Quantifying Drivers and Impacts

Jaia Syvitski – University of Colorado

Human energy expenditure in the Anthropocene (starting ~1950CE) is ~22 zetajoules (ZJ), and exceeds all human energy expended across the prior 11,700 years of the Holocene (at ~14.6 ZJ), largely through the combustion of fossil fuels. The global warming effect during the Anthropocene is more than an order of magnitude greater still. Global human population and their productivity and energy consumption are highly correlated and with most changes impacting the global environment: number of large dams; shrimp farming; industrial production of plastic, cement, ammonia, copper, gypsum, salt, iron, steel, sulfur, helium, aluminum; mineral species; atmospheric gases (CO2, N2O, CH4); terrestrial freshwater budgets; and surface temperatures, sea levels, and ice masses. This extraordinary outburst of energy and productivity demonstrates how it is that the Earth System in the past 70 years has departed from its Holocene state, forcing abrupt physical, chemical and biological changes to the Earth’s stratigraphic record that can be used to justify the proposal for naming a new epoch – the Anthropocene.

The world’s most unloved sedimentary structures: a new process model for flutes and tool marks

Professor Jeff Peakall – University of Leeds

Aggradational bedforms, from dunes to cyclic steps, are the subject of dozens of papers each year, producing lots of startling discoveries. These bedforms tell us about the flows that formed them and in turn aid interpretation and prediction. In contrast, sole structures have been almost entirely neglected for 50 years; unloved, ignored, and whose only role is to tell geologists which way the flow went. Here we present a new process model of flutes and tool marks in deep-marine environments that tackles a host of long-standing conundrums, and examines under what flow types these structures form. We finish by looking at the implications of the work including a revised Bouma Sequence diagram.

An Introduction to Virtual Outcrops and Virtual Fieldtrips in a time of Global Lockdown

John Howell, Simon Buckley, Nicole Naumann, Magda Chmielewska - Virtual Outcrop Geology Group, University of Aberdeen, and NORCE Research Bergen

A Virtual Outcrop (VO) is a 3D photorealistic model of a cliff or quarry that captures the geological features. Most recently, model sharing across the web has become possible through generic sharing sites such as Sketchfab and purpose-built sites like V3Geo.com. In this presentation we review the history for virtual outcrops and briefly discuss how they are collected, processed and how to access data that is available for public usage. We will then take a short virtual fieldtrip to the Book Cliffs of Eastern Utah, primarily to illustrate some of our learnings on the topic. We will conclude with a short discussion on the mechanics of how to build a VFT using publicly available data in LIME.

What can novel mixed sand-mud bedforms tell us about cohesive sediment gravity flow behaviour in the fringe of submarine fans?

Megan Baker – University of Durham

Bedforms are a key tool to reconstruct sedimentary processes in modern and ancient environments. This talk will present novel mixed sand-mud bedforms which have different shapes and sizes compared to pure-sand bedforms, and are found in the fringe of submarine fans. These striking mixed sand-mud bedforms are interpreted to be produced by sediment gravity flows with transient-turbulent fluid dynamics, due to the presence of cohesive clay. The presence and spatial trends in mixed sand–mud bedform types may be an important tool in interpreting fan fringe environments.

Microplastics in sedimentary systems. What we know and don’t know about this new type of sediment particle

Dr Florian Pohl – Durham University

The threat posed by plastic pollution to ecosystems and human health is under increasing scrutiny and the amount of mismanaged plastic waste entering the environment is growing at a staggering rate. In particular microplastics (plastic particles <1 mm in size) have been discovered in every sedimentary system on the planet and thus became a new type of sediment particle. As such, sedimentology represents an important and powerful tool to understand and predict the transport, dispersal, and ultimate fate of microplastics in different environments. However, due to the complex shapes and low densities the transport and sedimentation behavior of this new sediment particle may differ significantly from those of natural sediments. The presence of microplastics in the environments poses new challenges for the field of sedimentology, but may also provide opportunities to better understand the dynamics of sedimentary systems. In this talk I will provide an overview on global plastic-pollution, microplastic as a new and unique sediment particle, and on microplastics in seafloor sediments.

Building big bioherms from humble Halimeda: insights from a modern analogue

Mardi McNeil – Queensland University of Technology

The Halimeda algal bioherms of the Great Barrier Reef, Australia represent the largest living, actively accumulating Halimeda deposits worldwide. Following the Holocene post-glacial marine transgression, these bioherms kicked off the outer-shelf carbonate factory some 2000 years earlier than the nearby coral reefs. Recent multi-disciplinary work has revealed new insights into their surface geomorphology, subsurface architecture and depositional environment that may be of interest to those working on their fossil counterparts.

Magnitude and drivers of short term sea level fluctuations in the Cretaceous: a review

Dr Franz van Buchem and Dr Andy Davies – Halliburton – Landmark

Based on a recent review of the literature a data base of absolute values of short term (<3my) Cretaceous sea level rises and falls has been created. This shows an overall amplitude range of 5 to >65m, organised in four broad trends. The potential of aquifer eustasy has been investigated using climate modelling which showed a maximum impact of 5 to 10 meters. This leaves Glacio-eustasy as the key driver for short term high magnitude sea level changes in the Cretaceous.