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Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle Rock, Gove County, Kansas, USA) 1 (39149527591).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle Rock, Gove County, Kansas, USA) 2 (39119284452).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 10 (38295848745).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 13 (27395285329).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 14 (39172136501).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 17 (39145345792).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 18 (38465035604).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 19 (25307401698).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 20 (24311760997).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 21 (39172088881).jpg - Ser Amantio di Nicolao

Chalk (Niobrara Formation, Upper Cretaceous; bluffs south of Castle rock, Gove County, Kansas, USA) 22 (39172080551).jpg - Ser Amantio di Nicolao