Geological studies have identified three strata on the right of the Saint Maximin site, from top to bottom they are:
• Lutetian limestone
• Sables de Cuise (a type of marine sand from the Eocene)
• Sables de Bracheux (Thanetian)
In this area of the south of the Oise the relief was already a landmass during the Eocene area and it isolated a huge bay, known as the Thérain syncline, from the rest of the Eocene sea.
In the Saint Maximin basin substantial limestone deposits accumulated, eventually surpassing a depth of 20 meters..
The exploitable part of the Saint Maximin deposit is from the upper Lutetian age of the Eocene epoch. It lies above lower Lutetian sand and below nummulite limestone (known as “pierre à liards, after a small French coin).