Named as lowermost of six members of Laketown Dolostone (redescribed). Type section is at Tony Grove Lake, for which unit is probably named, SW1/4 SW1/4 of unsurveyed sec 6, T13N, R3E, in Bear River Range, northeastern Cache Co, UT, Wasatch uplift. Outcrops at numerous mountain ranges in western UT and eastern NV, Great Basin province. Consists of light-gray to grayish-black, microcrystalline to finely crystalline dolostone; thin to very thick bedded; weathers dark brownish gray to light gray; some parts are laminated and banded and others contain intraformational conglomerate. Deposited in intertidal and shallow subtidal, relatively high-energy environments. Thickness at type is 625 ft; averages 350 ft. Overlies Fish Haven or Ely Springs Dolostones (both redescribed); underlies High Lake Member (new) of Laketown. Measured sections. Silurian age [basis of age not discussed].

Source: GNU records (USGS DDS-6; Denver GNULEX).

Reexamination of Lakeside Mountains section of Budge and Sheehan (1980) resulted in revision of contact between Fish Haven and overlying Laketown Dolomites. Lakeside Mountains section is located near Delle, UT, in NE1/4 SE1/4 sec 32, T2N, R8W, Tooele Co, Great Basin province. Units 16-18 of Budge and Sheehan reassigned from Tony Grove Lake Member of Laketown to Bloomington Lake Member of Fish Haven. Revised thickness of member is 114.5 m (from 188.0 m of Budge and Sheehan). Basis of reassignment is 1) lithology of upper part of unit 18 is similar to upper part of Bloomington Lake at type section in Bear River Range, ID, and 2) unit 19 contains Silurian brachiopod VIRGIANA UTAHENSIS which is common in Tony Grove Lake. Disconformably overlies Bloomington Lake Member of Fish Haven and Floride Member of Ely Springs Dolomite. Underlies High Lake Member of Laketown. Early Silurian (Llandoverian) age.

Source: GNU records (USGS DDS-6; Denver GNULEX).