050219c

Limestone of the Knox Group, cross-section of a gastropod shell, mostly filled with lime mud (dark color like the surrounding matrix), remaining open space filled with calcite cement (clear and pink). Thin section, Kemper County Mississippi, approximately 3 miles below the surface.

022819b

Flute marks on Ordovician deep-water flysch, upstate New York, coin for scale.

Sole Man

Professor Lai Zhiyun points to sole marks, specifically flute casts, on the underside of an upturned bed of Ordovician deepwater flysch. Upstate New York.

Breaking Rock

Actually, this rock broke back in the Devonian Period. The white stuff is gypsum, which filled the spaces among the pieces of shattered rock, forming a new fabric and creating an altered rock that is called breccia. The light gray layer underneath is much older. It is Ordovician, and the surface in between represents an immense amount of time. This kind of surface is called an unconformity.

Rock

Been tweeting these beauties for days. This one is pink calcite & zoned dolomite cement in a crack in Cambro-Ordovician Knox dolomite. 1/2 a billion years' non-stop fun.

Some pictures of rocks