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Ancient Alluvial FansLook closely at the rock exposed in the canyon walls. Notice that the layers are composed of rocky debris that ranges in size from boulders to fine-grained sand and silt. Where have you seen similar sediment? These layers of poorly sorted conglomerate were deposited six million years ago on an ancient alluvial fan. The loose material was subsequently buried and cemented into solid rock known as the Furnace Creek Formation. More recent uplift and erosion have exposed them to view. At the time that these rock layers were being deposited, Golden Canyon and the modern basin of Death Valley had not yet formed. What was the source for the material that composes these ancient alluvial fans? These layers of conglomerate become thinner and disappear further to the east. The type of rock material that composes these conglomerates also indicates that the sediment came from the west. It's thought that the source was part of the bedrock of the Panamint Mountains; the modern counterparts of the ancient fans you are looking at are the gigantic fans of the Panamint Mountains that you observed from the mouth of Golden Canyon. The narrow, deep shape of the side canyons of Death Valley indicate that the uplift of the mountains is relatively recent, consistent with other evidence that the landscape of Death Valley is quite young. These relatively rare flood events are so dramatic that their effects can even be noticed within the brief span of a human lifetime. Such geologic forces have been carving the canyons of Death Valley for millions of years, constantly sculpting and changing this desert landscape. |
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