Two sedimentary rock formations dominate Golden Canyon. The yellow, mustard-colored sediments are the Furnace Creek Formation that consists dominantly of soft mudstone deposited in a basin or lake setting in the early to middle Pliocene Epoch (about 3 to 5 million years ago). The upper reddish, cliff-forming strata is conglomerate of the upper Furnace Creek Formation (representing alluvial fan deposits that prograded into the basin beginning about 3 million years ago). In many ways, this ancient basin is analogous to modern sedimentary basins forming in the Death Valley region today, however, fossils in the sediments suggest the region was wetter, supporting a variety of large mammals adapted to savannah-like conditions.