Renewable energy infrastructure, whether on- or offshore, requires in-depth understanding and accurate characterisation of the underlying geology.  Developers increasingly need detailed geospatial observations of the seabed and shallow subsurface, which are critical to the siting and design of offshore infrastructure such as submarine cables and offshore wind turbines. This is certainly true in the Bristol Channel, which is home to the second largest tidal range in the world. This high-energy environment has attracted much interest around the use of the seabed for tidal power and the potential to produce electricity from wave energy.

To support policy- and decision makers in this region, BGS has released an enhanced seabed geology map of the Bristol Channel, almost four times the size of the original, which extends from Carmarthen Bay to Newport and further south to the coast of Somerset.

Beyond offshore infrastructure, these maps also directly contribute to understanding of marine ecosystems, coastal management and defence activities. The data provides crucial information to those ensuring the port facilities along this coastline meet the requirements for these development opportunities.

As the UK transition to renewable energy gathers pace, these maps will become increasingly valuable to industry and stakeholders with an interest in developing clean energy, from offshore wind to tidal streaming, and in carbon capture and storage.

The successful implementation of offshore renewable energy projects and technologies and the development of ports in South Wales require a detailed understanding of the seabed. This new, expanded, fine-scale seabed map of the Bristol Channel will be an invaluable resource for developers, providing access to high-quality, detailed observations of the seabed geology that is vital to these kinds of developments.

Beyond its critical role in supporting the renewables sector, the map will also be useful to other data users, such as those involved with supporting marine ecosystems, coastal management and defence activities. It will also provide evidence for policy- and decision makers in the region.

Rhian Kendall, BGS Chief Geologist for Wales.

The map, featuring combined bedrock, sediment, bedrock structure and seabed geomorphology data, is available from BGS under the fine-scale maps section of theand is designed to be viewed at 1:10000 scale, or online as downloadable shapefiles. For information on licensing the downloadable GIS data (ESRI format), please contact digitaldata@bgs.ac.uk.

Understanding how heat moves within the subsurface is important for the development of geothermal energy, including ground-source heat pumps. Determining which geological areas are suitable for their installation is vital. For the first time, scientists at BGS have used time-series data at the , which is run by BGS, to look at long-term trends for subsurface heat.

The geo-observatory monitors 62 boreholes, 49 of which were observed every 30 minutes for four years between 2014 to 2018. The analysed data found previously undetected, localised cracks in the geology in the south of the city, where the subsurface is largely clay at that depth. These newly discovered cracks, which can be caused by plant roots, provide pathways that act as recharge routes underneath the south of Cardiff, allowing rain water to enter and be conveyed to the groundwater below.

While a ground-source heat pump can be highly efficient, installing one in one of these newly discovered areas of cracks could lead to performance issues. Specifically, the constant influx of cooler groundwater could hinder the heat pump’s ability to extract heat effectively and the system could potentially affect the groundwater flow and quality.

For geothermal developers looking to install shallow ground-source heat pumps underneath the capital, it’s important that this new data is carefully considered. The research shows that installing a ground-source heat pump in Cardiff deeper than 8 m will help to maximise the technology efficiency. 

Using time-system data for the first time in Cardiff has provided vital information to further our understanding of what lies beneath our feet. The discovery of geological recharge pockets in an area where they were previously not thought to occur is an important consideration for future infrastructure projects. It essential that geothermal developers take this research into account before installing a shallow ground-source heat pump, to ensure it runs as effectively as possible and is not impacted by recharge.

Ashley Patton, engineering geologist at BGS and research lead.

For more information about the Cardiff Urban Geo-Observatory please email 51ÁÔÆæ Cardiff (bgswales@bgs.ac.uk).

Detailed subsurface information is required to increase the uptake of geothermal energy technologies. This will contribute to UK net zero targets through decarbonisation of heat, along with energy security. The legacy UK geothermal catalogue is a significant compilation of data to inform geothermal assessments.

The comprises data contained in numerous historic technical reports from the 1977 to 1991 Geothermal Energy Programme. This was delivered by BGS and funded by the then UK Department of Energy and the European Commission.

The digital release contains 11 821 data points derived from 743 sites, comprising 77 per cent of the legacy geothermal catalogue dataset held by BGS. Alongside this, have been released onto the . Future releases of the legacy data are planned, for which the intellectual property rights (IPR) and validation checks are more complex.

This open release of the legacy geothermal catalogue makes a significant dataset more accessible, to support the development of geothermal energy and heat decarbonisation onshore UK. It may be used to inform pre-feasibility stages of projects or for research and innovation. The user guide describes acknowledged limitations of this first release of a legacy dataset. The aim is for future releases to include more recent data.

Dr Alison Monaghan, BGS Head of Geothermal.

This data is released under the and is a step towards Recommendation 3, , of the 2023 Deep Geothermal White Paper.

The data release comprises of a series of that can be accessed for use under the Open Government Licence, with the acknowledgement ‘Contains 51ÁÔÆæ materials © 51ÁÔÆæ 2024’.

51ÁÔÆæ has produced a for the (CMIC). It is a national-scale assessment of the geological potential for critical raw materials (CRMs) in the UK. It represents one of the first steps in the UK Government critical minerals strategy, which aims to make the UK more resilient to disruption in critical mineral supply chains by accelerating the growth of domestic capability.

CRMs are those minerals that are economically important, like those needed to make the batteries and semiconductors that are vital for the clean energy transition, and that are at the greatest risk of supply chain disruption. The UK has 18 metals and minerals on its CRM list, with another six materials classed as having elevated criticality. These are almost exclusively obtained from mining and refining operations in other countries, although tungsten has been mined in the UK in recent years.

Critical raw materials in the UK

51ÁÔÆæ has identified large parts of the country as prospective for CRMs. The key areas identified as ‘particularly worthy’ of more research are:

• an area around Loch Maree near Gairloch, Scotland
• parts of the central Highlands and Aberdeenshire, Scotland
• areas in mid-County Tyrone, Northern Ireland
• parts of Cumbria, England
• parts of the North Pennine orefield, England
• north-west Wales
• Pembrokeshire, Wales
• south-west England

Mining in the UK has a long history and many of the prospective areas have been mined before. For example, the LlÅ·n Peninsula of North Wales was mined for many years for manganese, which was originally important for steel making. In the future, the manganese deposits could be important for battery production.

Dr Kathryn Goodenough, co-author and BGS Principal Geologist.

51ÁÔÆæ used a mineral systems approach, which relies on the concept that minerals of a certain type are formed by a combination of particular geological processes. The team identified the geological processes necessary to form CRM deposits and mapped these criteria against the UK available datasets, which include maps of the geology, soil and sediment geochemistry, and mineral occurrences.

‘Potentially prospective’ doesn’t mean inevitable mining

The report authors stress that identifying an area as prospective does not necessarily mean it will be targeted for exploration and mining.

Our report identifies the parts of the UK where the geological criteria have been met and therefore have the potential for deposits to occur. There are no guarantees.

The report focuses on the geological evidence and does not consider potential constraints on development, for example where there are areas of outstanding beauty, villages and towns, or other environmental considerations.

Much more research is required and, if prospectors find evidence of commercially viable CRM deposits, they will have to go through the well-established planning process. Only one in a thousand potential mineral exploration projects ever becomes an operating mine.

The areas we have identified, along with other parts of the UK, are underexplored and we need more systematic research to understand the potential availability of CRMs in our country.

Eimear Deady, BGS Mineral Resource Geologist.

The UK and mining

Mining in the UK stretches back to prehistoric times. Currently, gold, barite, fluorite, gypsum, potash and polyhalite are among the minerals being mined. Exploration for many raw materials is occurring across the whole of the UK.

Some CRMs, like lithium, tin and graphite, are typically the primary products of mines. Others are produced as co- or by-products.

Where mining develops for other commodities, it is always important that miners also assess the potential for CRMs in their deposits.

Other countries like Canada, the USA, Norway, Sweden and Finland are also mapping their own geological potential as they too understand the risk of continuing to rely entirely on global supply chains for minerals that are absolutely vital to our way of life.

Dr Kathryn Goodenough.

list names key geological sites of international scientific relevance that have made a substantial contribution to the development of geological sciences through history.

The UK sites are:

• Siccar Point, Scotland
• Giant Causeway and Causeway Coast, Northern Ireland
• Moine Thrust, Scotland
• Ynys Llanddwyn Mélange, Wales

The selections have been made from right across the world and include other well-known sites such as the Grand Canyon (USA), Sugar Loaf Mountain (Brazil) and Mount Everest (Nepal). Whilst many have helped to develop the science of geology, others are the world best examples of geological features and processes.

The list was drawn up by the International Union of Geological Sciences (IUGS), one of the largest international geoscience organisations in the world, together with UNESCO.  

The identification of the top 100 sites was part of a project that involved more than 200 specialists from almost 40 nations and ten international organisations.

There were a number of sites from across the UK put forward as part of the list, with nominations coordinated by representatives from BGS and the environment agencies from the four regions of the UK.

Dr Kirstin Lemon of the Geological Survey of Northern Ireland (GSNI) was among the panel of international experts to evaluate more than 181 nominated sites.

It fantastic that the international geoscience community has given visibility to these sites, which recognises their importance for the development of geological science.

These sites are some of the world best demonstrations of geological features and processes and contribute to our understanding of the Earth formation through time. Now they are officially recognised as holding the highest scientific value.

Dr Kirstin Lemon, GSNI.

The full list of global sites will be revealed at a special IUGS event in Spain this week.

Siccar Point

Siccar Point, off the coast near Eyemouth, Scotland, is a world-famous place of geological interest. Its historical importance was established in 1788 by James Hutton, when he discovered the near-vertical layers of sedimentary rock, which enabled him to describe deposition, folding and erosion, some of Earth most fundamental geological processes that form the landscapes we know today. Hutton account, according to Scottish Geology, describes Siccar Point as ‘looking so far back into the abyss of time’.

Giant’s Causeway and Causeway Coast

The Giant Causeway and Causeway Coast World Heritage Site was selected primarily for its role in the development of geology as a science, representing a key site in proving the origin of volcanic rocks during the 18th century. It was nominated jointly by GSNI, the Northern Ireland Environment Agency and Trinity College Dublin due to its importance.

Moine Thrust

The Moine Thrust is the main geological structure in the North West Highlands, made up of a sequence of Precambrian metasedimentary rocks. Known informally as ‘the Moine’, it has attracted geologists from all over the world for well over a hundred years. The site is the focus of many influential studies, all helping to advance understanding of structural geology and thrust tectonics. It was here in the early 1880s that Charles Lapworth demonstrated that the sequence of rocks was not a simple stratigraphic order, but was repeated by folds and faults.

Ynys Llanddwyn Mélange

The Ynys Llanddwyn Mélange is part of Newborough National Nature Reserve and Forest and located within the GeoMon UNESCO Global Geopark. ‘Mélange’ is the name given to the chaotic body of mixed rocks at this location including limestone, cherts and pillow lavas . It was here that the term was first used, over 200 years ago, and debates as to how mélanges form are still ongoing to this day. 

Anglesey (Welsh: Ynys Môn) follows the Bristol Channel as the second in a series of new fine-scale maps that contain combined bedrock, sediment, bedrock structure and seabed geomorphology data.

The maps are based on data produced by UK Civil Hydrography Programme of the Maritime and Coastguard Agency, which includes bathymetry data, backscatter imagery, grab samples and other existing datasets such as seismic, sediment texture sheets and existing 1:250000-scale geological maps.

These new resources provide important evidence for policy and decision makers, who need to consider the increasing demands being placed on the marine environment from recreation, marine conservation and protection, fishing and resources (e.g. aggregates). The data may be of particular interest to developers of tidal stream energy devices wanting to deploy technology and infrastructure to create renewable energy and generate clean, low-carbon electricity, making Anglesey a hub for marine energy. 

Priority areas currently being mapped also include Yorkshire and East Anglia, with other areas being added as our fine-scale mapping programme progresses.

The seabed substrate around Anglesey forms a fascinating patchwork of bedrock, glacial deposits and more recent marine sediments. Remarkably well-preserved suites of drumlins can be seen on the sea floor in this area; these were moulded under the last ice sheet as it flowed towards the south-west. When the glacier margin retreated, icebergs began to break off, ploughing grooves that can now be seen on the seabed. Under modern marine conditions, strong currents have produced sand waves that can migrate across parts of the sea floor.

The maps are available from BGS under the fine-scale maps section of the  and are designed to be viewed at 1:10 000 scale or offline as downloadable shapefiles.

Other maps in this series:

• Bristol channel 1:10 000 map

51ÁÔÆæ has begun publishing a new series of high-resolution offshore geological maps showing the distribution of bedrock and sediments that make up the seabed around our coasts. Maps of the Bristol Channel and Anglesey were the first to be published, with further regions such as Yorkshire and East Anglia to follow as our mapping programme progresses.

This article takes a closer look at the seabed featured in the the first map of the series, which stretches along the central part of the Bristol Channel, from south of Swansea Bay in the west to Newport in the east.

The Bristol Channel

The Bristol Channel is a large estuary and river system that extends from the Celtic Sea eastwards to the limit of tidal influence along the River Severn at Gloucester. The channel separates South Wales from Devon and Somerset and has the second-largest tidal range in the world at Avonmouth, with a 12.3 m mean spring range ().

Bedrock geology

The seabed of the Bristol Channel is partially covered by soft sediments (superficial deposits) but much of the area is free of sediment cover, allowing for the detailed mapping and interpretation of bedrock units and features. The bedrock geology recognisable in the bathymetric data will be familiar to anyone who knows the coastline of south-east Wales, which is characterised by low, Carboniferous limestone cliffs surrounded by younger, Triassic- and Jurassic-aged rocks.

The bedrock geology presented on the new maps shows a pattern of small outcrops of highly fractured Carboniferous rocks of the , which would have formed a landscape of hills and valleys following uplift and erosion caused by the Variscan Orogeny. 

A window into the distant past

During the Triassic, this part of Wales was hot and arid with wadis, flash flooding and scree slopes () surrounding the hills and cliffs. The low ground in between featured lakes that deposited mudstones and periodically evaporated to leave salt flats (the ‘red beds’ of the ). These deposits sit unconformably on the Lower Palaeozoic landscape.

During the late Triassic and Lower Jurassic, a marine transgression, or rise in sea level, flooded the landscape. A series of deposits recording this event can be seen in the cliffs of the Vale of Glamorgan and traced off shore (). By the Jurassic, this part of Wales had become marine and units of the were deposited, including the, which is divided into the St Marys Well Bay, Lavernock Shales and Porthkerry members.The youngest bedrock unit identified is the , which records deposition in a shallow, sea-shelf environment.

All of these rocks were subsequently deformed, most likely by the Alpine Orogeny. This was a period of mountain buildingin central and southernEuropeandwest Asia. The orogeny resulted in a network of folds, fractures and faults that is especially apparent in the deformation and offsetting of the rocks in the well-bedded Porthkerry Member and Inferior Oolite Group.

Geological structure

The north-east to south-west orientation of the inner part of the Bristol Channel (which is included in the eastern part of our new dataset) and much of the Severn Estuary is influenced by the Severn Estuary fault zone. This is a dextral, strike-slip fault zone considered to have been active during the early Carboniferous. Comparable north-east to south-west trending faults have been recognised within the eastern part of the area covered by this dataset, where they dissect earlier-formed folds and offset the bedding within the Porthkerry Member.

However, within the central and outer parts of the Bristol Channel, the faults are dominated by:

• a set of west-north-west to east-south-east trending structures
• a locally complex network of north-north-west to south-south-east and north-north-east to south-south-west trending cross-faults

These structures have been digitised as ‘fault observed, displacement unknown’ due to the potential complexity and multiple phases of movement over time. There is also an absence of clear marker horizons or beds within, in particular, the Porthkerry Member.

The east to west trending faults are interpreted as forming part of the central Bristol Channel fault zone, a major fault system that is believed to have developed in response to the extensional reactivation of an underlying Variscan thrust during the Mesozoic. North-west to south-east trending faults within the Bristol Channel, including the Sticklepath–Lustleigh and Watchet (also known as Cothelstone) faults, are interpreted as older Variscan structures that reactivated in response to tectonic events during the Mesozoic and Cenozoic.

Superficial deposits

The superficial sediments identified within the dataset comprise marine deposits that include:

• gravel
• sand
• mud
• sandy mud
• sand and gravel
• mud, sand and gravel

The deposits of sand and gravel within the central part of the dataset are related to areas of potentially mobile sediment within the Bristol Channel. A range of bedforms associated with recent or contemporary marine processes within a tidal-dominated environment has developed upon these superficial sediments.

Linear, ribbon-like areas of sand-and-gravel are located along a marked channel incised into the bedrock, which denotes the course of the palaeo-River Severn and its tributaries. Smaller areas of sand occur to the north and south of this palaeo-river channel, where they occur on relatively flat to very gently dipping areas of bedrock, in particular in the area underlain by the well-bedded limestone and mudstone sequence of the Porthkerry Member.

In some areas, the sediment cover is relatively thin and the bedrock geology can be clearly seen or traced through these superficial deposits, or the superficial deposits are too thin to be clearly represented on a geological map designed to be viewed at the 1:10 000 scale. Consequently, only the more prominent, thicker superficial deposits have been captured (digitised) within the dataset, to provide the user with an indication of the main areas of potentially mobile sediment.

The superficial sediment cover at the eastern end of the mapped area is typically finer grained (mud and sand), reflecting its location within the inner part of the Bristol Channel.

An area of gravel and sand-and-gravel exposed at the north-western end of the dataset may represent a submerged, shallow, coastal sequence, with the sands and gravels infilling an irregular network of tidal channels. The coarse-grained nature of these deposits may, at least in part, result from the subsequent removal (winnowing) of fines (mud) by tidal currents within the high-energy environment of the central Bristol Channel.

The modern channel

The present-day geomorphology of the seabed across the Bristol Channel is influenced by events that occurred throughout the Quaternary. Evidence of fluvial processes is found in the form of the palaeo-River Severn channel and its tributaries. These palaeo-channels are incised into the bedrock in the central and inner parts of the Bristol Channel, with their margins denoted by marked breaks in slope (both convex and concave).

The floors of the larger channels are locally covered by sand and/or gravel, with well-developed bedforms on the surface of these superficial deposits. The predominantly north-to-south trend of the crestlines of the sand waves is consistent with the superficial deposits being variably reworked by tidal currents flowing parallel to the central axis of the Bristol Channel.

Breaks of slope within the largest channel marking the main course of the palaeo-River Severn are considered to mark the variably degraded edges of former river terraces. Elsewhere, the surface of the superficial sediments and bedrock is relatively smooth or incised by long, linear, positive and negative features formed as a result of scouring of the seabed by strong bottom currents.

Accessing the data

These maps are available from BGS under the fine-scale maps section of the  and are designed to be viewed at 1:10 000 scale.

Downloadable data is also available via a commercial data licence, but fee-free for academic research, use by registered charities, or in connection with emergency or civil contingency incidents.

For details please contact iprdigital@bgs.ac.uk.

New combined bedrock, sediment, bedrock structure and seabed geomorphology maps are available from BGS under the fine-scale maps section of the and are designed to be viewed at 1:10 000 scale or online as downloadable shapefiles.

Based primarily on data produced by UK Civil Hydrography Programme of the Maritime and Coastguard Agency and made available by the UK Hydrographic Office, they are of relevance to offshore developers who require a detailed understanding of the geology of the seabed. The maps include bathymetry data, backscatter imagery, grab samples and other existing datasets such as seismic, marine conservation zones, sediment texture sheets and existing 1:250 000-scale geological maps.

As the UK transition to renewable energy gathers pace, these maps will become increasingly valuable to industry and stakeholders with an interest in developing clean energy, from offshore wind to tidal streaming, and in carbon capture and storage.

The first area to be published this month features a central section of the Bristol Channel, from Swansea Bay to Newport, which is home to the second largest tidal range in the world. The high-energy environment of the channel has attracted much interest in recent years for the use of the seabed for tidal power schemes, including tidal power schemes that have the potential to produce electricity from wave energy.

Adopting renewable energy and technologies requires a deep understanding of the seabed and so developers have a growing need for access to bathymetric data, enabling more detailed observations of seabed geomorphology that are central to such evaluations.

As well as being of use to offshore developers, the release of our new maps will benefit all kinds of applications: marine spatial planning, technological research and development, fishery resource management, environmental impact studies and climate change models, providing evidence for policy and decision makers.

Prof Emrys Phillips, BGS Quaternary and Glacial Scientist.

While mapping the seabed has been a major challenge for marine geoscientists over the years, the development in acoustic technologies has allowed for the collection of more, and much better resolution, data in much less time.

51ÁÔÆæ has plans to release a suite of high-resolution maps in the future, including offshore Anglesey, Yorkshire and East Anglia, and further areas will be added to as its marine mapping programme progresses.

This is a great example of using the excellent high quality freely available data collected under the CHP for a different reason from its original purpose and gaining extra geological insights and value from the data.

Mary Mowat, BGS Marine Data Manager