Irchester Old Lodge Pit

Also within

Northamptonshire County

Condition (Natural England)

Geology & landscape

Geological Period: Jurassic · Rock Type: Limestone

Description

Area, 0.4ha 0.99ac Description Irchester Old Lodge Pit exhibits a section from the top of the Rutland Formation up to the Blisworth Clay, including one of the only two complete White Limestone Formation sections in Northamptonshire. Particularly distinctive here is the junction between the basal Kallirhynchia sharpi Beds and the upper part of the formation; this is the equivalent junction to that seen in Oxfordshire between the Shipton Member subcontractus and morrisi Zones and the overlying Ardley Member hodsoni Zone. The White Limestone above the junction is often very fossiliferous, containing a rich molluscan fauna with associated brachiopods and echinoids. In addition, these limestones locally exhibit very fine crossbedding and related sedimentary features. The White Limestone has yielded Aphanoptyxis bladonesis Arkell, a gastropod which enables correlations to be made with the equivalent strata of Oxfordshire and Gloucestershire. The lower part of the Blisworth Clay is important because it has here yielded only freshwater palynomorphs ‘spores’; in all other areas there are indications of a marine transgression at or near the base of the Blisworth Clay and its equivalents. This is a key Middle Jurassic locality important for the information it yields on both Bathonian environments and stratigraphy.