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If you enjoy the talk and are interested in becoming a member then take a look at our membership page.
We normally meet on the 2nd Thursday of the month, except for August. From March to October we have face-to-face meetings which are held at Redbourn Parish Centre. The talks are on a wide range of Earth Science topics, given by people who are experts in their field.
Over the winter months, November to February our meetings are via Zoom.
HGS members can view talks that the speaker has kindly permitted us to record. Links to these talks are shared in our HGS member's monthly 'Chalk Board' Newsletter.
Please check our Calendar for full details of our exciting 2026 programme of talks.
Guests are welcome, for a small charge.
2026
2026
12 February
12 February
talk on the End-Triassic mass extinction and its aftermath
given by Professor Paul Wignall, School of Earth and Environment, University of Leeds
Abstract
The end-Triassic marks one of the big 5 mass extinctions of the fossil record and is also probably one of the least understand. It has many things in common with the preceding mass extinction at the end of the Permian. Both are associated with the eruptions of vast flows of basalt lava and both occurred whilst the world’s continents were united into a supercontinent. The talk will focus on some of the latest discoveries and ideas regarding both the mass extinction event and its aftermath. Unlike some other crises, the recovery from the crisis was remarkably quick in a geological sense and it of course paved the way for dinosaur to dominate the planet for 135 million years.
12 March
12 March
AGM
followed by refreshments & launch of the Hertfordshire 50th anniversary book – Mike Lambert & Nick Pierpoint
9 April
9 April
49th Percy Evans Lecture on Snowballs in teh Desert - A Glacial History of Oman
given by Ross Garden, Reading Geological Society
Ross is kindly standing in for the scheduled speaker Dr Haydon Bailey. Haydon’s talk will now be given at a later date.
A Cryogenian glacial valley fill, Arn Formation, near Mirbat
Abstract
The Earth has experienced repeated major icehouse periods through its history. Across the UK, we have many examples of the Plio-Pliestocene ice age deposits and in Scotland we see evidence of Pre-Cambrian Snowball Earth glaciations. Sowhat might the Sultanate of Oman on the eastern margin of the arid Arabian Peninsula offer?
Oman lies on the Tropic of Cancer and the current climate is hot and arid with midday winter temperatures in the mid 20’s and summer temperatures reaching 40° C and above. The arid climate, together with the relative ease of movement and hospitality of the Omani people provides a geological wonderland. There are many geological delights in Oman, but the area provides a variety of geology resulting from previous glaciations. We can see evidence for Proterozoic marine glaciations together with lacustrine deposits from the Permo-Carboniferous ice ages. The lack of vegetation and long geological history of the area provides good out crops of the glacial formations and allows examination of lateral facies variations that typify these deposits.
But the Oman also contains evidence of the impact of high latitude glaciations on land masses at low latitudes. The Omani Plio-Pliestocene history is characterised by ice driven sea level falls and rises, compressed climatic zones and cooler and wetter periods. As Arabia is situated between Africa and Asia these climatic changes are likely to have impacted the migration of homids out of Africa.
Glacial dropstone in Permian Al Khlata deltaic sandstones, Huqf
14 May
14 May
Talk on Geology of Stonehenge and the bluestone controversy
given by Prof. Peter Worsley, Emeritus Professor of Quaternary Geology, University of Reading
Abstract
Stonehenge has recently come into the public eye due to the publication of the results of new geochemical work. The Sun newspaper declared ‘Mystery of where the giant rocks came from SOLVED’ whereas The Guardian was more cautious with a headline ‘Archaeologists discover likely source of Stonehenge’s giant sarsen stones’. The senior English Heritage properties historian said that she was delighted that one of the most intriguing questions about Stonehenge had been answered. The background to this ill-judged euphoria will be critically examined and the geological fundamentals reviewed.
Apart from the sarsens, the other geological problem lies with the assemblage of ‘foreign’ rocks incorporated into the henge structure, i.e. the so-called Bluestones. There now appears to be little doubt that the Bluestones are primarily derived from outcrops in south-west Wales but the mechanism whereby they arrived to Salisbury Plain are far from being resolved. Most archaeologists have accepted the hypothesis that Neolithic people were responsible for the transport of the lithostats from their source to the plain but over time the favoured routes have changed drastically. In contrast geologists have been split between those who accept the human transport mode and those who favour natural earth surface processes as being responsible for transportation – glaciation. The strengths and weaknesses of these competing ideas will be assessed.
11 June
11 June
Talk on The Chalk Sea Ecosystem Project
given by Dr James Witts, NERC Postdoctoral Fellow in Palaeoecology, Natural History Museum, London
Abstract
The onshore Chalk Group of the United Kingdom provides a continuous and well-exposed rock and fossil record spanning the Late Cretaceous (Cenomanian – Maastrichtian stages, ~100 - 72 Ma). As an economically important resource, the chalk has been quarried and studied for >200 years and a detailed stratigraphic framework is available. The sequence is abundantly fossiliferous, recording every marine trophic level from nanno- and phytoplankton to benthic and nektonic molluscs and apex predators. Key events recorded in the Chalk include carbon cycle perturbations during the middle Cenomanian and across the Cenomanian – Turonian boundary (Oceanic Anoxic Event 2 – also associated with peak Cretaceous climate warming and a biodiversity crisis), the highest global sea-levels of the last 250 myrs during the Turonian, and a long-term climate cooling which culminates with the coldest temperatures of the Late Cretaceous during the Maastrichtian.
The Natural History Museum, London (NHMUK) alone contains >55,000 UK Chalk Group macrofossil specimens, including rare taxa and material from now inaccessible localities. Only a fraction of these have been published or are available in public datasets. Many specimens contain limited metadata, and ages or stratigraphic position are poorly constrained. To unlock these ‘dark data‘ we are re-dating >1,500 macrofossil specimens using calcareous nannofossil biostratigraphy. Combining these with data from new fieldwork, we are conducting the first ‘whole ecosystem‘ study of the functional diversity and ecology of the Chalk Sea, providing an unprecedented record of the effects of global Cretaceous climate change on marine ecosystems at a
variety of temporal and spatial scales, all within the same depositional system.
Biography: I trained as a geologist with an MEarthSci degree from the University of Manchester (2009), completing a PhD on the Cretaceous-Paleogene (K-Pg) mass extinction event in Antarctica with the University of Leeds and British Antarctic Survey in 2016. I then hopped ‘across the pond’ for a Lerner-Gray Postdoctoral Research Fellowship at the American Museum of Natural History in New York (2016-2018) and a postdoctoral position at the University of New Mexico in Albuquerque (2018-2020), studying Cretaceous and Paleogene macrofossils and ecosystems in the US Gulf Coast and Western Interior. After a stint as Lecturer in Palaeontology at the University of Bristol (2021-2023), I moved to the NHM as a NERC Postdoctoral Fellow in Palaeoecology in September 2023.
9 July
9 July
Talk on Researching the Puddingstone Book
given by Gerald Lucy, Essex Rock & Mineral Society & Mike Howgate, AGS & HGS.
3 September
3 September
Talk on The Deep Geology beneath southern England
given by Dr. Chris Pullen, Director, CP Exploration
Weald View
Abstract
An extensive well and seismic database provides an understanding of the Mesozoic and Tertiary evolution of Southern England, but deep Palaeozoic structures remain poorly defined due to limited well penetration and weak seismic imaging below the Triassic.
Removing the gravity effects of post Permian sediments highlights residual
anomalies that suggest deeper Palaeozoic architecture. Three major features emerge: the Southwest England Anomaly, linked to Variscan right lateral terrane translation; the South Coast Anomaly, interpreted as a thickened Palaeozoic thrust complex; and the Central England Anomaly, where Lower Palaeozoic rocks occur at relatively shallow depths.
8 October
8 October
Book Presentation – The meteorites
given by Helen Gordon, Hertfordshire University & Author
ARRIVAL
A glint in the blackness. A tear in the fabric of a heavy curtain covering a bright window.
Move closer. The glint becomes denser, finds form. Colours emerge. A blue-white-marbled ball.
Move closer. Land appears, sandy, rose-tinged, burned with gold, covered with pale branching tendrils. The ball becomes a dome edged with electric blue.
Move closer. The soft inky brown of mountains. Rock folded over and over itself like a crumpled silk scarf. A world falling into focus. A body falling through the exosphere, the thermosphere, the mesosphere, the stratosphere, the troposphere.
Move closer. The dark green shadow of the valley. Bright lines of water. Patchwork fields. Arterial roads and grids of houses. A sign: If you live here, you’d be home by now.
Move closer. A car. A house. A child on a picnic blanket. The land rushes up too fast. Earth flies up like water
12 November
12 November
Zoom talk on Critical minerals from geology to circular economy: a matter of national security
given by Associate Prof. Kathryn Moore of Exeter University
Abstract:
With the imminent release of a new Critical Minerals Strategy, the UK is updating its approach to national security. In this lecture, I will highlight the security issues that threaten critical mineral supply chains into the UK and into most countries. I will explain how mitigation of the risks requires groundtruthing, based on an understanding of geology and material properties, as well as wider socioenvironmental and political considerations. I will discuss how the needs of critical minerals production is a challenge in terms of skills requirement, and why the discipline of geology has never been more important.
10 December
10 December
Zoom talk on The history of geological thought and exploration of the geology of the Himalaya
given by Dr. Danny Clarke-Lowes, Director, Nubian Consulting
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