With Purse Caundle having a complicated geological background, and this author not being a geologist, it is somewhat difficult to adequately describe this aspect of the area. The character around the Purse Caundle area is an amalgam of the Fuller's earth Clay vales and ridges, and being followed by the Forest Marble/Cornbrash ridge, all from the Middle Jurassic era, being laid down at the bottom of the sea probably about 130-140 million years ago. The Fuller's Earth gives rise to low profile land-forms.
In his unpublished M.A. thesis of the 1980s, Rural Landscape of the Blackmore Vale circa 1840, John Chiplen went into some detail as to the geology of Purse Caundle. In his Chapter Four, the section 'Parishes on the Fuller's Earth Clay Vales and Fuller's Earth Rock - Forest Marble Escarpments' he mentions the three mile wide zone between the Inferior Oolite and the Cornbrash outcrop. This zone consists of two parallel Fuller's Earth Clay vales and double scarp, the lower scarp being formed by the Fuller's Earth Rock and the higher scarp by the Forest Marble. Purse Caundle lays completely within this zone, with the village centre and outlying western and southern farmsteads located on the Fuller's Earth Rock scarp crest.
Represented as outcrops in Purse Caundle in various degrees is a 30-55 metre layer of Forest Marble, and below this is 45-65 metres of Frome Clay, followed by 66-110 metres of Fuller's Earth. This wide Fuller's Earth Rock outcrop is from the Middle Jurassic period, being displaced southward by the large fault that runs southward from Poynington, continuing through Purse Caundle at Toomers Hill, and northwards, east of Milborne Port.
The fossils in the Fuller's Earth Rock include several distinctive brachiopods (a marine animal with two shells, but different from a bivalve). The stone is blue-hearted or pale cream, and does not weather as well as the Inferior Oolite further west around Sherborne, though it has been used for several farm buildings in Thornford and Bere Hackett, and possibly Sir Walter Raleigh's 'new' Castle. East of Sherborne there were several quarries at Crendle and Trips Farm. Trips Farm is entirely built of the Fuller's Earth Rock, and it can also be seen in some of the walls of Purse Caundle manor house. This Fuller's Earth has contained sufficient water for local uses, with the wells, streams and ponds in and around the village getting a good supply from the rock.
There is also the stiff brown clay soil of the later Forest Marble, on which lie the villages of Lillington and Leweston on an escarpment which runs to Purse Caundle on the borders of Stalbridge.
One geological snapshot can be taken along the A30 road from Toomers Hill, which descends and crosses a valley cut in the Upper Fuller's Earth. The road then runs north of Purse Caundle village and through a gap cut by a headstream of the River Yeo at Crendle Corner through a low ridge on the underlying Fuller's Earth Rock. This forms a west-facing escarpment, from wooded Crendle Hill on the north which becomes bolder on wooded Hanover Hill to the south. The Upper Yeo valley then follows into Lower Fuller's Earth Clay.
The characteristics of land use, and settlement patterns, are obviously determined by the type of soil. In Purse Caundle it was thus mainly the heavy clay soils of Frome Clay on the eastern part and of the Lower and Upper Fuller's Earth - as can be testified by this author when metal-detecting on Church Farm.
The precise geology of the area can be found in the British Geological Survey 1:50,000 Series map, Sheet 313, Shaftesbury. From this it will be seen that Church Farm has quite a mixed geology. From East to West there are several strips of soil types running North-South. Coming down hill from the Stourton Weston road there is firstly a band of Forest Marble Clay; then a very narrow strip of Wattonensis Beds; then a slightly wider Upper Fuller's Earth; and finally a wide band of Fuller's Earth Rock which goes as far as and beyond the road running down from the A30 road to the village centre.
Home Farm and Manor Farm are predominantly this same Fuller's earth Rock up to Hanover Wood, with narrow strips of Upper Fuller's Earth plus Bowden and Acuminata Beds.
Trips Farm is predominantly Frome Clay with some Wattonensis Beds, with the farm buildings on Upper Fuller's Earth.
Rue Farm is also predominantly on Frome Clay.
At the sale of the manor house in 1920, the soil description was given in the sale catalogue as being limestone and clay, with subsoil of clay and gravel.
A low ridge of Fuller's Earth Rock cradles Milborne Port. This limestone ridge is remarkable for its wildlife habitat with herb-rich grassland containing stemless thistle and pyrimidal orchard alongside semi-natural ancient woodland at Hanover Wood, Crendle Hill Wood and Everlanes Covert. This feature peters out near Stowell in the Fuller's Earth clay vale which is distinguished by smaller pastoral fields often waterlogged with marshy reed and sedge filled ditches. Willow trees line the watercourses. Hedges are species rich, and elm regenerates well.
Much mention has been made of Fuller's Earth. This is a high absorbent claylike substance consisting of hydrated aluminium silicates, which is used predominantly in 'fulling' (shrinking and thickening) woollen cloth - a process introduced by the Romans. It is also used in talcum powder, in cosmetics and skincare, and as a filter such as in a fining for clarification of beer in the cask or keg. It is capable of absorbing large quantities of grease, and soaks up oil; and is also used as cat litter.
The very small limestone outcrops gave rise to several known old now disused lime kilns around the village, with their accompanying quarries:
1. Just south of Gospel Ash Farm (ST 6926 1889) - illustrated as beginning of this post.
2. Just north of Crendle Corner (ST 6905 1825).
3. At Crendle Corner (ST 6905 1815).
4. North-west of Trips Farm (ST 688 168).
5. South-west of Trips Farm, off Goathill Road (ST 6848 1597).
6. Rue Lane, south of Trips Farm (ST 6844 1586) - see two illustrations below.
Over the years the British Geological Survey has carried out several borehole examinations around the parish:1. Hanover Hill (ST68770 16700) 60.9 metres. 1933. ID 389854(*)
2. Trips Farm (ST 69200 15900) 6.09 metres. - - - ID 389844(*)
3. Crendle (ST 69090 18370) 0.00 metres. - - - ID 389855(*)
4. Toomer Hill (ST 69850 18200) 1.00 metres. 1977. ID 389834
5. Toomer Hill (ST 69920 18230) 2.00 metres. 1977. ID 389835
6. Toomer Hill (ST 69930 18280) 2.00 metres. 1977. ID 389836
7. Home Farm (ST 69590 17580) 70 metres. 2007. ID 18142158(*)
(*) Possibly also in association with boring for water - see Section 3 below.
Borehole drilling was also carried out at Church Farm in 1990, at Grid Ref: ST 70120 18260 (ID 391890). It was bored through 139.48 metres of Bathonian to Toarcian strata. It started in Frome Clay, goingv through the underlying types of Fuller's Earth, Inferior Oolite, and in to the top of the Bridport Sands. See the British Geological Survey Research Report SA/93/01 (illustrated below), which goes into great detail, even to the extent of identifying fossil remains. This latter aspect may also be found in Geology of the Country around Weymouth, Swanage, Corfe and Lulworth, published by HMSO 1947. Other borehole details may be found on the website www.bgs.ac.uk/geoindex.
The remains of the prehistoric sea-water loving crocodile found in the Fuller's Earth Rock north-west of Trips Farm show testimony of the original state of the land in this vicinity - see CHAPTER 2. 
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