Abstracts Session 1
Dr Tim Pharaoh
Honorary Research Associate
British Geological Survey
An integrated petrogenetic and petrophysical model for the crustal structure of Southern Britain: farewell to the Charnwood Terrane
The late Precambrian volcanic and sedimentary basement of Southern Britain is known from several small, widely-dispersed and tectonically-controlled outcrops. Deep boreholes sample further basement diversity. The challenge has been to map these different components and establish their relationships. Aeromagnetic data from the 1960s, of similar vintage as the East Midlands Geological Society, still provide the best hope of reaching this goal. A new inversion model provides valuable insights into the depth and structure of magnetic components of the basement. This 3D model of the crust can be sliced in any orientation, generating vertical cross-sections and horizontal depth slices and that can facilitate mapping and interpretation.
Another aspect of the new work is the recognition that the present day North Island of New Zealand provides an excellent analogue for Southern Britain 565 million years ago. The Hikurangi destructive margin incorporates a subduction trench, arc and oceanic marginal basin. Calc-alkaline volcanos of the Taupo Zone occupy an extensional wedge projecting into the juvenile NZ crust while the Taranaki volcanos occupy the back-arc region. The tremendous diversity of volcanic rocks within this small area of NZ is compared to the basement of Southern Britain, and we will see how this modern analogue can help us understand the complex geology of, and establish an internally consistent crustal model for, Southern Britain in late Precambrian time.
Another aspect of the new work is the recognition that the present day North Island of New Zealand provides an excellent analogue for Southern Britain 565 million years ago. The Hikurangi destructive margin incorporates a subduction trench, arc and oceanic marginal basin. Calc-alkaline volcanos of the Taupo Zone occupy an extensional wedge projecting into the juvenile NZ crust while the Taranaki volcanos occupy the back-arc region. The tremendous diversity of volcanic rocks within this small area of NZ is compared to the basement of Southern Britain, and we will see how this modern analogue can help us understand the complex geology of, and establish an internally consistent crustal model for, Southern Britain in late Precambrian time.
Dr Stu Clarke
Lecturer in Basin Analysis and Sedimentology
Keele University
‘Earth, Fire & Water’: New insights into the evolution of the Carboniferous succession (Alston Formation) of northern England
Lecturer in Basin Analysis and Sedimentology
Keele University
‘Earth, Fire & Water’: New insights into the evolution of the Carboniferous succession (Alston Formation) of northern England
Repeated successions of limestone, siltstone, sandstone and coal – Yoredale Cyclothems – are characteristic of the Carboniferous succession of northern England. Cyclothems are defined lithologically, but crudely represent shallowing- upward successions from normal regression in a marine-marginal setting. The repetitions are typically attributed to Milankovitch-style cyclicity, but the extent to which this is a factor, compared to ‘on-planet’ controls such as accommodation, sedimentation and auto-cyclicity, is equivocal.
We combine fieldwork, geophysical data from core, and cyclo-stratigraphical techniques, to provide new insight into the controls upon the evolution of strata of the Alston Formation. Preliminary results indicate cycles that correlate with signatures from planetary orbitals, some of which may be tentatively attributed to Milankovitch cyclicity. These include cycles that correlate to the Yoredales, but also to longer timescales that may explain unconformities, and to shorter timescales that may provide explanation for additional cyclicity observed within parts of the succession.
The work provides a framework for interpolation below seismic resolution, and within and between the sediments of coeval environments. These scales are important to the energy transition as ‘reservoirs’ become ‘basinal’ in scale and sealed by lateral facies changes with coeval systems (e.g. ‘deep saline’ CCS) and fluid flow questions are regional (e.g. lithium).
We combine fieldwork, geophysical data from core, and cyclo-stratigraphical techniques, to provide new insight into the controls upon the evolution of strata of the Alston Formation. Preliminary results indicate cycles that correlate with signatures from planetary orbitals, some of which may be tentatively attributed to Milankovitch cyclicity. These include cycles that correlate to the Yoredales, but also to longer timescales that may explain unconformities, and to shorter timescales that may provide explanation for additional cyclicity observed within parts of the succession.
The work provides a framework for interpolation below seismic resolution, and within and between the sediments of coeval environments. These scales are important to the energy transition as ‘reservoirs’ become ‘basinal’ in scale and sealed by lateral facies changes with coeval systems (e.g. ‘deep saline’ CCS) and fluid flow questions are regional (e.g. lithium).
East Midlands Geological Society is a registered charity in England and Wales, number 503617.
© COPYRIGHT East Midlands Geological Society 2025. All Rights Reserved.