Bathtub Ridge

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mn
Ore minerals manganese minerals; pyrolusite; psilomelane; rhodochrosite

Geographic location

Quadrangle map, 1:250,000-scale DP
Latitude 69.1
Longitude -142.3
Nearby scientific data Find additional scientific data near this location
Location and accuracy Accurate to within 915 meters (3,000 ft). Grybeck, 1977, p. 42, Locality 10.

Geologic setting

Geologic description

About 53 meters (175 ft) of highly manganiferous beds crop out in the middle the of pebble-shale member of the Lower Cretaceous Kongakut Formation which is 158 meters (520 ft) thick at this locality. This manganiferous section is black, with small pellets and thin beds of sedimentary manganese carbonates; exact chemical composition of this interval not known.
The term Kongakut Formation is no longer widely used; the interval described here is currently referred to as the pebble shale unit and is widely recognized in the subsurface of northern Alaska. The pebble shale unit depositionally overlies the Kemik Sandstone of Early Cretaceous age. At Bathtub Ridge the pebble shale unit depositionally underlies siltstone (see Bird and Molenaar, 1987, Figure 5.6 A) whereas north of Bathtub Ridge, the pebble shale unit depositionally underlies shales of Early Cretaceous age, some of which are radioactive and tuffaceous.
Geologic map unit (-142.302676008178, 69.0997867332498)
Mineral deposit model Sedimentary manganese of Cannon and Force (1986, p. 231).
Age of mineralization Age of host rocks is Early Cretaceous.

Production and reserves

Workings or exploration Analysis of samples indicated about 5 percent Mn.
Indication of production None

Additional comments

USBM OF 63-78, p. 21, Locality 23 was listed as a reference prior to the last
review of this file. This reference was not verified by Kelley.