EVIDENCE OF HIGH ENERGY DEPOSITION IN BASAL NOONDAY FORMATION (A CAPSTONE CARBONATE), KINGSTON RANGE, SE CALIFORNIA

In the Kingston Range region, southeastern California, Noonday Dolomite sits directly atop lithologies of every underlying formation. On every lithology the contact tends to be undulatory – with 2-20 foot wavelengths and 0.5 to 3 foot amplitudes. Lower amplitude undulations are observed on metamorphics and higher amplitude undulations on Beck Spring Dolomite.

On every lithology, the basal Noonday locally contains clasts of the underlying lithology. Cobble-sized clasts are found up to 20 stratigraphic feet into typical Noonday lithology. Two Beck Spring Dolomite megaclasts have been located in the lower Noonday – a 2' x 12' clast above Excelsior Mine and a 35' diameter clast northwest of Crystal Spring Mine. When above a Beck Spring Dolomite contact the clasts are extremely angular and display some jigsaw-puzzle-like structure. When found above typical conglomerate of the Kingston Peak Formation, the clasts tend to be more rounded. Atop metamorphics (near Winters Pass) and the Crystal Spring Formation (near Excelsior Mine) typical Noonday dolomite is separated from the underlying lithology by a conglomerate which tends to become more clast-rich at depth. The matrix of the upper two to three feet of this conglomerate appears to be dolomite similar to typical Noonday. In the rare occasion when the conglomerate is thicker than this, it assumes a typical Kingston Peak lithology below the top two to three feet. In most of its exposures the Noonday sits directly atop cobble and boulder conglomerates of the Kingston Peak Formation. When it does, the undulatory highs appear to be beveled and the Noonday/Kingston contact is abrupt. The undulatory lows tend to be filled or partially filled with a Noonday-matrix-supported conglomerate.

The basal Noonday in the Kingston Range is interpreted to be a high-energy carbonate debris flow which ran out over a hummocky Kingston Peak Formation surface punctuated with extruding megaclasts. The debris flow beveled Kingston hummocks and re-mobilized Kingston clasts to create the basal Noonday conglomerate with Noonday matrix. The debris flow grooved the surface of lower-lying megaclasts and explosively ripped off pieces of higher-standing megaclasts of Beck Spring Dolomite.