Field work in the San Juan Basin has primarily included the relocation of nonmarine molluscan type and referred specimens published by Stanton (1916) from the field studies of C.M. Bauer (1916) and Bauer and J.B. Reeside, Jr. (1921).

Upper Cretaceous freshwater mollusks are relatively common in the Fruitland Formation. This view includes two horizons, one at the slope change from drabs grays to lighter whitish yellows and one at the base of the brown-colored channel sandstone to the right (Hartman photo C03522).



Slabs of oriented elongate unionids are present in the Fruitland Formation at a number of localities, but it is difficult to get such large bedding surfaces exposed (Hartman photo C03494).