Geologic description
Goldbottom Creek was placer mined for gold at least as early as 1900 (Brooks and others, 1901). Moffit (1913, p. 87) reported that hand mining and a small hydraulic plant operated in the upper part of the creek in 1905. Moffit (1913) also reported stream tin (cassiterite) at several places in the creek. Goldbottom Creek was later worked by small-scale mechanical methods. Mining perhaps was in conjunction with small-scale mechanical mining on Silver Creek (NM094) and Steep Creek (NM093). Silver Creek and Steep Creek, also Grouse Creek (NM099), are eastern tributaries of Goldbottom Creek. Production on Goldbottom Creek is unknown, but was fairly small. Some small-scale mining and prospecting have been carried out in recent years. Goldbottom Creek drains the basal contact of the massive marble unit mapped by Hummel (1962 [MF 248]) and Bundtzen and others (1994). One of the compilers (C.C. Hawley) mapped this section of Goldbottom Creek at 1 inch to 1,000 feet in 1995 and identified several possible structures that could source gold above the head of placer pay. About 1,000 feet above the head of the placer deposit, Goldbottom Creek enters a canyon, and flood-plain gravels are too thin and narrow to be exploited except on a very small scale. Approximately 6,000 feet above the placer, the creek crosses the lower contact of massive marble and is in this unit for about 2,000 feet. In this reach of the canyon, the marble is highly dolomitized and cut by small quartz veinlets. The marble is in a synclinal structure, and the basal contact is cut again by Goldbottom Creek in its northern headwaters. About 3000 feet above the upper basal marble contact, Goldbottom Creek crosses part of the Penny River fault system that hosts the California prospect (NM062). The possible sources of placer gold in Goldbottom Creek include the complexly veined dolomite unit, the sheared basal contact zone of massive marble, and veins associated with the Penny River fault system. Moffit (1913) reported granitic boulders in Goldbottom Creek gravels, so some gold may have been derived from reworking of glacial deposits derived from the Kigluaik Mountains. |
