A HYMENOPTERAN BROODING CHAMBER FROM THE COLERAINE FORMATION (UPPER CRETACEOUS, CENOMANIAN) OF THE MESABI IRON RANGE DISTRICT OF NORTHERN MINNESOTA

The Coleraine Formation of northern Minnesota, based on its invertebrate fauna, has been correlated with the lower most part of the Benton Group. The invertebrate fauna suggests a near shore, inter tidal marine environment at or near the southern most end of the Hill Annex Mine area. To the north and east the sediments grade from coarse, cemented conglomerates to loosely cemented sandstone abundant in invertebrate fossils. Numerous erosinal channel deposits cutting through the sediments suggest an estuarine environment as does the presence of the estuarine crocodile Teleorhinus (Terminonarious) mesabiensis, fresh water turtles, fish and carbonized wood and plant material. In the original material collected in 1928 were abundant marine invertebrates, vertebrate marine faunas, Ophiomorpha burrows and one internal mold of a bee (Hymenoptera, Apoidea) brooding chamber showing evidence of tidal infillings. The bee brooding chamber (cell) belongs to the ichnofamily Celliformidae, and possibly represents a new ichnogenus/species. The morphology of this bee cell, characteristic of solitary nest architecture, represents one of the oldest bee trace fossils yet discovered.