NEW INSIGHTS OF THE CRETACEOUS DEPOSITS (CENOMANIAN) IN THE MESABI IRON RANGE DISTRICT OF NORTHERN MINNESOTA

The Cenomanian age Cretaceous deposits of Northern Minnesota have been mentioned in Minnesota Geological Survey reports and, in differing degrees, in other papers since 1899. These deposits, of varying thickness, are primarily reported from the Mesabi Iron Range District as extending approximately 114 kilometers from Coleraine, Minnesota eastward to the Enterprise Mine near Virginia, Minnesota with isolated outliers south in the Cayuna Range. In the past 116 years no serious study has been undertaken to correlate this data with recent core samples and other evidence from new mining operations in this area. Nearly all of the Cretaceous deposits mentioned in earlier reports have been “mined out”or are flooded and are long since lost to stratigraphic investigation. The most famous and useful site at the Hill-Annex Mine in Calumet, Minnesota contains an extensive in-situ section of the Cretaceous which will be under water within five years due to the rising water table in the mine pit. With new mining opportunities as well as access to data from most of the previous 400 mining localities along the Mesabi, a useful stratigraphic record can now be made of the Coleraine Formation in and around the Mesabi District.