Chalk is the most available building stone in north Lincolnshire. In the example shown above (some surviving old farm buildings in Barton parish) squared blocks of chalk laid in courses and bonded by lime mortar have survived intact, while nearby chalk rubble has been used in another part of the wall not coursed and bonded with much lime mortar (just visible). To achieve the blocks the chalk has been cut against the ‘grain’, this not possible with many chalk strata. The density of chalk varies from strata to strata, the denser the strata the more resistant is the rock to chemical and mechanical weathering. Locally the best building chalk comes from the strata identified by geologists as the Lower Chalk (logically so as it will have undergone the greatest compaction), that strata at the northern end of the Lincolnshire Wolds being 75-80 feet thick.
The following quote is taken from an article written by A. Russell about Elsham Top Farmstead in the book Tyszka, D. Miller, K. and Bryant, G. Land, People and Places (Lincolnshire County Council, 1991, 168-169) – ‘A local method of preparing chalk for building was to set aside the hardest blocks and leave them to dry outside for two to three years. Those not destroyed by frost action were used for building. At Elsham, due to the exceptional hardness of the chalk, … the octagonal chalk columns to the cartshed have remained in good condition’.
St. John’s church Croxton, near Barnetby, N. Lincs., was built of chalk blocks in the 13th and 14th centuries, with some of that walling surviving.
Although I haven’t yet checked the geological map, presumably the chalk strata at the southern end of the Yorkshire Wolds quarried for building stone for Meaux Abbey in the 13th century was Lower Chalk (see Part 1).