The Little Falls Dolostone has been defined and described inadequately at its type section at Little Falls, in the Mohawk Valley, New York. The main mass of the formation extends from Poland on the west to Randall on the east. I consider the immediate Little Falls area to represent the type locality, within which is a composite type section of six localities.

The formation, 400 ft (122 m) thick at Little Falls, is well known for its "Herkimer diamonds" (quartz crystals) and "cryptozoons" (algal stromatolites). Dolostone predominates, but sandstones and mixed dolostone-sandstone varieties are common. Gray colors, medium to thick bedding, and vuggy beds are characteristic. Glauconite, chert, and silicified ooids are commonest in the upper part. Calcite is a minor and late paragenetic constituent. Fossils are extremely rare.

Four subdivisions, informally designated as "units," herein are recognized above the nonconformable contact with the underlying Proterozoic gneiss. Unit A, the lowest subdivision, is 90 to 100 ft (28 to 30 m) thick and has conglomerate and sandstone at its base overlain by coarse-crystalline dolostone. Unit B consists of about 200 ft (61 m) of dark, fine to medium-crystalline dolostone with many vuggy beds; within the unit is a unique sequence of alternating algal-stromatolitic dolostone and sandstone. Unit C, 25 to 40 ft (7.6 to 12.2 m) thick, is primarily coarsely crystalline glauconitic dolostone containing quartzose intercalations. Unit D, characterized by very fine-crystalline dolostone, is 30 to 40 ft (9.1 to 12.2 m) thick, and contains reddish-gray zones and silicified ooids; i grades upward into the Tribes Hill Formation (Lower Ordovician) at Little Falls.