Marvel Creek has been extensively placer mined over about 3 miles, or most of its length. It is in a non-glaciated valley with headwaters in an area where the Upper Cretaceous granitic stock of Marvel Dome is surrounded by hornfels in sedimentary rocks of the mid-Cretaceous Kuskokwim Group (Box and others, 1993). A small undated felsic stock is bedrock at the head of the placer workings. Hornfels near the intrusive rocks is locally cut by abundant quartz stringers and veins up to 8 inches wide. Some iron-staining accompanies the quartz veins, but metallic minerals are not obvious (Maddren, 1915, p. 341).Marvel Creek valley has not been glaciated. The alluvium is moderately well sorted but locally derived, coarse, and subangular. Silt is present in the gravels and a discontinuous yellow clay horizon is present on or near bedrock. Pay is on bedrock and in bedrock fractures, or on the clay horizon where it is present. There are discontinuous sloping bench deposits that are incised by the active stream along lower parts of the creek. The lower creek also incises bedrock, and the initial discovery of gold in 1911 was on bench bedrock exposed in a cutbank there (Maddren, 1915, p. 343). Along the present flood plain, the gravel deposits are about 800 feet wide and 5 to 25 feet thick. It appears that they thicken upstream; near the head of mining a 60-foot deep shaft failed to reach bedrock (Maddren, 1915, p. 342). The creek has been placer mined over 3 miles of its length. Most of the mining on the lower part was by a small dredge. Mining took place almost every year from the 1920s to 1940 and recommenced after WW II until at least 1970 (Hoare and Cobb, 1977). Much of the pay ranged in grade from 0.01 to 0.02 ounce of gold per square foot and much of the gold was coarse (Hoare and Cobb, 1977, p. 19). In 1912, a 20,000-square-foot open cut completed with pick and shovel recovered about 0.03 ounce of gold per square foot (Maddren, 1915, p. 344).