What winter erosion exposed on the bluff's south-eastern face is a midden, the ancient equivalent of a kitchen midden or refuse deposit, where coastal communities discarded the shells of shellfish they had eaten. These accumulations, modest and unglamorous, are among the most informative archaeological features a coastline can offer.

The deposit here runs for 6.45 metres along the cliff face and sits as a distinct lens, thickest at its centre at around half a metre, tapering away to the north-east and south-west. It is composed predominantly of limpet shells, with occasional periwinkles and mussels mixed in. Above it lies a layer of light brown sandy loam roughly a quarter of a metre deep, topped with a thin veneer of modern soil. The shell layer itself contains horizontal clasts of sandstone at varying levels, some of considerable size, along with a sharp, clean contact at its base, suggesting the deposit was laid down deliberately or at least accumulated in a stable, bounded environment rather than washing in from elsewhere. Perhaps the most intriguing feature lies directly beneath the shell layer, clearly separated from it: a lens of iron-cemented loam of similar shape and thickness, in which five vertically placed and regularly spaced stones are visible. The regularity of those stones implies human arrangement rather than natural deposition. Below that, lighter sandy loam with angular boulders rests on bedrock. The site came to wider attention in June 2016 when geologist Andrew C. Phillips, of the Illinois State Geological Survey, observed it during a study of local geology and noted the shell layer extending along the cliff face with its characteristic loose composition and structured base.