Bucks Geology Group
Grid reference: SP 890 510 (for the church).
Ordnance Survey map: Northampton and Milton Keynes Sheet 152.
Geological maps: 1:50,000 series Bedford sheet 203.
Bucks County Council administration area: Milton Keynes.
Owned by: Public and private. Many listed and protected buildings.
Area of site: n/a.
Access, location and parking: Easy access via the A509 and easy parking at many locations.
Interest Summary: Olney town centre buildings, church and grave stones. This is an excellent locality to see local building materials put to their best use. Many characteristic rock types can be seen including sedimentary structures and fossils.
The geological story starts as you approach Olney. Here the flat and featureless landscape of the Jurassic clays (from the Oxford Clay in the Milton Keynes area to Lower Lias clays in the Olney area) transforms into the harder limestone ridges outside Olney. Landscape shows a direct geological control in this area. The softer rocks wear down to form the vale and the harder rocks form the ridge and hills. This is also true of the effect of the Ouse as it flows through this part of the valley, cutting its valley and leaving behind a series of previous terraces.
Olney is a pretty little town using much of the Jurassic limestones of the area. Buildings using the Blisworth Limestone and/or Upper Liassic limestones are: the Cowper Museum, the Parish Church of St Peter and St Paul (see photos below), the Olney Centre (which used to be the old Victorian school, below), the Old Maltings, and numerous private houses, walls and rockeries in the village along Bridge Street, the Market Place and Weston Road. All the characteristic features of the rock types can be seen including lithology, sedimentary structures and fossils.
The church of St Peter and St Paul. The church is particularly interesting geologically as it uses a mixture of all types of local rocks: Liassic limestones, newer (Victorian) Portland Limestone repairs, ironstones, sandstones and a large calcite block (source unknown). Other rock types can be seen in the church graveyard: more local limestone, but also Italian marble, Peterhead Granite (from Scotland) and Dartmoor Granite (from Devon
Granite from Scotland - one of many exotic rocks in the churchyard.
The gate to the Church of St Peter and St Paul, Olney. Many different limestones have been included in this gate pier, some local and others from Lincolnshire or Bath, as repairs were needed.
The gate piers are an interesting mixture of several repairs as stone masons struggled over the years to make a good match to the original Blisworth Limestone used in the original structure and most of the surrounding walls. Weldon, Portland, Bath and Blisworth Stone can all be found in the structure. Although they are all Jurassic limestone,, they weather very differently resulting in the varying colours and amount of decay. The Portland Limestone for instance is the palest block (not labelled) and becomes paler with weathering and age.
The Church Hall, Olney