Argillite, shaped in the form of ellipsoidal linear structure, Central Andes, Peru

Whereabouts

Yauli Dome area, central Peru.  I collected this while working with Lou Lepry and  Ralph Rogers in Peru in ~1980, where Lou was doing his thesis work near Morococho and Ralph was doing PhD work at Cerro de Pasco.   It was a terrific day, working at ~16,000 ft and bundled up in a parka.  The ellipsoidal projectiles were lying on the ground all over, as if we had stumbled upon an ammunition storage bunker.   I like the ballistic shape of this structure, and how it speaks to an environment of constrictional flow during deformation.  I wish I had collected more of these things.

Age & Formation
Devonian Excelsior Formation, ~375 Ma.