Figure 9. Paleogeographic map of the Carlin basin area during its early stages of formation. Shown are late Eocene highlands (estimated from page-size figure in Haynes, 2003), possible early-basin normal faults, and the distribution of the basal fluvial unit of the Humboldt Formation, which was the first Miocene unit to be deposited in the basin. Shown also is the approximately outline of the Carlin gold trend (yellow lines), from which numerous Oligocene to early Miocene supergene alunite dates were obtained.