Cordilleran Section - 108th Annual Meeting (29–31 March 2012)

Paper No. 8
Presentation Time: 08:30-18:30


STOCKTON, David R., PO Box 482, Big Pine, CA 93513,

Originally following a southeasterly path across a flood basalt covered upland surface, the paleo Cottonwood Creek (CC) passed south of Station Peak to join Crooked Creek and then down into Deep Springs Valley. Extreme base level change along the Fish Lake fault, eastward tilting of the White Mt block (Stockli+ 2003), and exposure of a buried granite paleotopography resistant to a southward stream course, led to a stream capture event which redirected CC north of Station Peak to flow down across the Fish Lake fault into Fish Lake Valley.

The resultant headward pulse of incision into the Cottonwood Plateau (CP) was concurrent with glaciation which left striations and erratics on an interfluve below Barcroft Station. Granodiorite tors below Barcroft Station retain traces of a smoothed sculpted outline as if they were frost shattered roches moutonnes.

The upper CP forms a shallow basin, drained where CC breached a resistant band of Reed dolomite. Between Sheeps Pass and Mt Barcroft, lay an extensive ice field held back by this dolomite ridge (DR) which extends north of Patriarch Grove. Most ice drained around the DR down the North Fork of CC with ice overrunning the DR in two saddles W and NW of Eva Bell mine, leaving a piedmont moraine complex in upper Cottonwood Basin. Opposite the north end of the DR ice overflowed a saddle into the McAfee Creek drainage.

Ice in later glacial episodes did not reach such levels, at least in part due to drainage entrenchment. Even without ice overflowing the DR, windblown snow from the upper plateau maintained cirques under the saddles near Eva Bell. Elliot-Fisk (1987) noted a pattern of reduced valley glacier length in later glacial advances, proposed an early ice cap upon the plateau NE of Mt Barcroft, and speculated that a growing Sierra Nevada rain shadow reduced later glacial development in the Whites.

Presently, windblown snow from the plateaus feeds valley head cirques (LaMarche 1965). Cold dry snowfall from north Pacific storms would favor wind transport. Moist snowfall from subtropical Pacific storms would hinder surface wind transport, favoring an ice cap. Uplift of the Transverse Ranges choked off subtropical moisture passing northward across the Mojave (Axlerod 1983). This storm path evades the SN rain shadow effect and would load the leeward NE slopes of Sheep and Paiute Mts, enhancing a CP ice field.