Cothill/Dry Sandford Pit

Site Location

Dry Sandford Pit is also known as Cothill Quarry (after the adjacent village).  The site is located at NGR: SU 468 995 about 1.5 km south east from the junction of the B4017 and Honeybottom Lane in the village of Cothill. The entrance is ca. 80 m south west of the junction between Honeybottom Lane and Church Lane.

SSSI

This site has been designated as a Site of Special Scientific Interest (SSSI) and is therefore protected under law.  It is forbidden to use a geological hammer on the exposures or to attemt to collect in situ fossil specimens.

Maps

British Geological Survey Maps:  

1:50 000    253

 

Ordnance Survey Maps:

1:10 000    SU48NC

1:25 000    170

1:50 000    164

Bed 8

The best exposure of the Urchin Marl (Bed 8) can be found along the trackway to the main quarry exposure.

Bed 7

This is coarse-grained, flaggy limestone.  A small amount of sand can be found within its recrystallised, sparry matrix.  The unit is unfossilferous.  Its flaggy nature is a result of weathering under pedogenic processes.

 

Bed 6

This is a coarse-grained, shelly brown sandstone.  A band of impersistent calcareous concretions runs through the centre of the bed.

Bed 5

Commonly known as the Upper Trigonia Bed, this is a coarse-grained, heavily bioturbated fossilferous-calcarenite unit.  It is relatively resistant in relation to the beds below and above.  In its base Thalassinoides burrows can be seen.

Bed 4

An unconsolidated, medium-grained orange sandstone with some cross-lamination.  The unit has horizons that are high in undifferentiated fossil material.  The boundary between this bed and the one above is particularly fossil rich, containing echinoids, bivalves and ammonites.

Dry Sandford Specimens from the MNH

Collection:

Chlamys nattheimensis

Nucleolites scutatus

Trigonia reticulata

Cardioceras densiplicatum

Perisphinctes sp.

Thamnastria concinna

Bed 3

Commonly known as the Lower Trigonia Bed.  Variable in thickness, this coarse-grained unit is highly fossilferous throughout. In places the fabric is sandy and there are persistent concretions. The errosive base is irregular and pebble-rich. The fabric grades up into a pure, white oolite horizon at the top of the unit. 

Bed 2

The first bed to be observed in the main exposure.  It is an unconsolidated, medium-grained sandstone.  The grains are well-sorted, clean and mature.  At the top of the bed you'll find infrequent calcareous doggers. The entire bed (including the doggers) is unfossilferous.

Bed 1

The oldest rocks exposed at Dry Sandford can be found at the edge of the fen.  The rocks are in situ but patchy.  They are a fine-grained calcarenite.  The top horizon of the unit is highly fossilferous, featuring bivalves (e.g. Trigonia) and brachiopods.

A glossary of some words used here.

brachiopod

Brachiopods are shelled,  marine animals (not molluscs) belonging to their own phylum: Brachiopoda.

 

calcarenite

A sandy limestone

 

concretion

A mass of mineral-cemented rock grains.  Sometimes referred to as a 'dogger'.

 

pedogenic processes

The various processes that occur within, or in contact, with soil.

 

Thalassinoides

A trace fossil of a burrowing organism.

FOCUS ON

Dry  Sandford

This video was shot to accompany this web page.

 

Iona Horton and Hugo Thould are both members of Oxford Geology Group and were keen to help showcase this geologically important location.

 

The film is a visual 

vade mecum to the Jurassic, Oxfordian Stage exposures at

Dry Sandford.

From the
OGG Film
Archive

This film was made by H.C.H. Crawley, the first Chairman of the Oxford Geology Group, in 1958.

 

It shows an OGG Field Party visiting Dry Sandford Pit at Cothill.  The character of the exposure at Dry Sandford is particularly well shown in this black and white film

 

The film was obviously shot well before the site was protected.  These days hammers and collecting specimens from the exposure is prohibited.