Upon This Rock: the geology of Broadland churches

Figure 1. It used to be suggested that round church towers, such as St Peter & St Paul’s Mautby (above) were necessary in areas where there was a lack of suitable building stone for producing “quoins” – the blocks usually forming the corners of a wall. Although flint is the most common building material in Norfolk churches, and it is not easy to shape, there are many examples locally of corners formed of flint or cobbles alone. Some were seen in the churches visited by participants, St Mary’s, Surlingham, for example.

Visiting a church can often reveal much about local customs and religious practices of former generations. Can they also provide an insight into history on geological timescales? A series of day-schools organised by the Broads Hidden Heritage project in 2021 aimed to find out.

The geology of the Broads has had a profound impact on the appearance of its local churches. Early churches were usually constructed from materials available in the immediate area. The preponderance of flint in the structure of churches in the Broads reflects the quantity that appears naturally in the topsoil across the region. Indeed, from a distance it can sometimes seem that flint is the only material making up the fabric of many Broads churches. However, closer examination often reveals an array of other types of stone.

Figure 2. Participants are introduced to the stones in the church walls at St. Mary’s, Fishley.

During a series of day-schools entitled ‘Upon This Rock: the geology of Broadland Churches’ – in July, August, September and October 2021 – participants visited various churches in different areas of the Broads to examine the stones that made up their walls. The days were led by two expert guides: Tim Holt-Wilson (Norfolk Geodiversity Partnership) and Ian Hinton (Norfolk Historic Buildings Group).

Figure 3. Tim Holt-Wilson (left) and Ian Hinton (right). Each of the Upon This Rock events began with presentations in a local village hall about the geology of the Broads and the architectural history of churches. The two experts then led participants on a tour of local churches.

Tim Holt-Wilson provided instruction and guidance on how to identify the various rocks. He also described the conditions in which some were formed, often millions of years ago, and speculated about the method by which they would have been transported to the Broads. Tim was keen to point out that the geology of Norfolk is complex. Much material was carried here by glacial ice or meltwater. In more recent times, much stone was deliberately imported, either for the express purpose of building or to act as ballast on trading vessels.

Meanwhile, Ian Hinton provided a commentary on building techniques and architectural styles. With his help, participants learnt the skill of how to ‘read a church’ to reveal its history. As different materials became available and religious practices changed, the churches themselves were adapted and altered. The design of arches, windows, buttresses, and numerous other features all give clues about their date of construction. Irregular patterns on exterior walls often provide evidence of more recent building work, or areas where previous features have been removed.

Figure 4. Participants gather round the tower to ‘read the church’ at St. Andrew’s, Stokesby.

While most of us remember the general categories of igneous, sedimentary and metamorphic rock from our school days, participants of the Upon This Rock events were soon on first name terms with dolerite, ferricrete, oolitic limestone, gneiss and a myriad of other specific varieties.

In some cases, it was possible to take a look at life in the deep past, as with the fossilised remains of serpulid tube worms from the Jurassic Era preserved in calcareous mudstone in the walls at St. Mary’s Church, Norton Subcourse; or at St. Andrew’s Church, Kirby Bedon, where the imprint of sea urchin shell is perfectly preserved in one of the flints.

Figure 5. Migmatite at St. Mary’s Church, Aldeby. This composite rock does not occur naturally in Norfolk and so must have been transported from elsewhere by some means. Tim Holt-Wilson suspects that this sample may have arrived on-board a ship as ballast, perhaps originating from Scandinavia.

More recent materials were no less intriguing. Roman brick has been reused in several churches and in some cases significant quantities of stone has been reused from buildings dating from the period of Roman occupation, as at St. John the Baptist’s, Reedham. Reused stone from other demolished ecclesiastical buildings is also readily apparent in the walls of the some of the churches visited.

Figure 6. Imprint of sea urchin shell in a flint at St.Andrew’s, Kirby Bedon.

In all, sixteen churches were visited during the four events (Fig. 7) providing a liberal coverage of the Broads area in Norfolk. The churches (and days they were visited) were:

Sat 24 Jul (Fig. 7, top row, left to right): St. Edmund’s, Acle; St. Mary’s, Fishley; St. Andrew’s, Stokesby; St. Peter & St. Paul’s, Mautby.
Sat 21 Aug (second row left to right): St. Peter & St. Paul’s, Tunstall; St. Peter & St. Paul’s, Halvergate; St. Andrew’s, Wickhampton; St. John the Baptist’s, Reedham; St. Botolph’s, Limpenhoe.
Figure 7. An internal wall at St. John the Baptist’s, Reedham. A notice states, ‘This area of wall has been left uncovered to show re-used Roman material, laid in a herring bone pattern. The church is built on the site of a large Roman building, possibly a fortlet. The grey stone from this building was later used for the walls and tower.’’
Sat 25 Sep (third row, left to right): St. Andrew’s, Kirby Bedon; St. Mary’s, Surlingham; St. Mary’s, Norton Subcourse; All Saints, Thurlton.
Sat 23 Oct (fourth row, left to right): St. Edmund’s, Fritton; St. Mary’s, Aldeby; All Saints, Wheatacre; St. Mary’s, Burgh St. Peter.