Geosphere; February 2008; v. 4; no. 1;
p. 36-74; DOI: 10.1130/GES00114.1
© Geological Society of America
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Figure 11. Photographs of middle Miocene sedimentary units in the Elko basin. A: Basal Miocene, epiclastic sand and conglomerate beds on the west side of the Adobe Range. Photo taken looking north along the western outskirts of Elko. The beds overlie more steeply dipping volcanic units of the late Eocene Indian Wells Formation (light-colored, below). The gentle eastward dip of the Miocene units may be nearly primary. B: Peko Hills (behind the green floodplain of the North Fork Humboldt River) and fluvial Miocene sediments (tan, foreground) on the eastern dip slope of the Adobe Range. The fluvial sediments continue across the river valley, underlie the low bench to the left (north) of the Peko Hills, and depositionally overlie Paleozoic rocks in the Peko Hills, indicating that the hills were paleohighs during sedimentation. The snowcapped peaks in the background are the Ruby Mountains. Late Cenozoic erosion of the Miocene strata during downcutting of the river has progressively exposed the Peko Hills. C: Conglomerate in an east-trending paleovalley north of Cedar Ridge (Fig. 10). The clasts were derived from Paleozoic units exposed in the Piñon Range to the west. When the channel filled, finer grained epiclastic sand and pebbles formed a continuous cover over the channel fill and adjacent bedrock areas. D: Pebble-rich fluvial sediments in the Huntington Creek area in the southern part of the Elko basin. All of the clasts are crystalline metamorphic and igneous rocks derived from the Ruby Mountains to the east. These fluvial beds overlie ash-rich lacustrine units along Huntington Creek. Arrow points to 6-cm pocket knife for scale. E: Ash-rich, thin-bedded lacustrine sediments in a railroad cut near Wells. Green beds to the right have been altered to chert and zeolites. An unaltered tephra from this sequence was dated at 10.5 Ma. Hammer in right-center of photo (arrow) provides scale. F: Horizontal Pliocene (ca. 2.1 Ma) lacustrine units (light, P) cover lowlands cut into gently west-dipping fluvial strata of the middle Miocene Humboldt Formation (M, tan in middle distance). Photo taken looking east-northeast at the Secret Pass area between the East Humboldt Range (left horizon) and the Ruby Mountains (to right of photo).
Copyright © 2008 by Geological Society of America
