This is from a thin section of Asbian age Carboniferous limestone, from apron reef near Castleton in Derbyshire. The field of view is approx 3.8mm. It seems to be 4 leaf-like structures branching out from a central mass of peloidal micrite. It is surrounded entirely by pretty coarse sparite which seems to be filling an old cavity. It's got me and my lecturer stumped... Anyone seen anything like this before?
GeologyRocks