A pit from which marl, a mixture of clay and carbonate of lime, is excavated. Marl is used as a fertilizer, among other things. Marl is a rock containing clay minerals and calcite, commonly mixed with other components such as silt.

Generations ago, farmers valued marl as a fertilizer for lime-deficient soils and as a soil conditioner for sandy soils. The lime in marl cements sand grains together, so the soil can better retain heat and water. When added to clay soils, marl had the opposite effect: soil particles became less cohesive, allowing more air, heat, water and plant roots to penetrate.

This marl, it would seem from the qualities which it possesses, promotes vegetation in all the different ways. It increases the food of plants; it communicates to the soil a power of attracting this food from the air; it enlarges the pasture of plants; and it prepares the vegetable food for entering their roots.

Coltishall Village dates back to Roman times, and in the middle ages it was a centre for the extraction of lime and marl, an industry that continued for many centuries. It was later replaced, when the river became navigable, by a thriving boat and Wherry building industry.

The year 1685 was when the first detailed mention of the River Bure as a navigation described goods being delivered to Mayton Hall (or Meyton Manor). Goods were carried from Great Yarmouth miles to Horstead Mill, just above Coltishall, where they would then be carried by land to towns such as Aylsham. It was also possible to navigate right up to Mayton Hall which still stands near the water's edge at Little Hautbois, about 1 mile upstream of Horstead. Marl (used as fertiliser) was the main cargo heading downstream. This came from the Mayton Hall estate and was distributed to farms close to the river.