Onnia superba Moroccan Trilobites Death Assemblage

This is SUPERB death assemblage of a member of the Order Asaphida, Family Trinucleidae from the Ordovician deposits of Blekos, Morocco known as Onnia superba. Cointained within this 6.7 inch by 5.7 inch matrix plaque are TEN examples of the type 0.5 inch - 0.8 inch wide at the genal spines. This is a NATURAL occurence, NOT a composite. There are many fine details present, such as the tiny occipital spine and the fine pitted cephalic ring. The trinucleids made their living by kicking up detritus from the seafloor, filtering it through the cephalic ring. What catastrophe resulted in this mass death?

Also see: Moroccan Trilobites