Arikaree Group sandstones over Brule Formation clays (Miocene-Oligocene; Chimney Rock, near Bayard, Nebraska, USA) 9 : 無料・フリー素材/写真
Arikaree Group sandstones over Brule Formation clays (Miocene-Oligocene; Chimney Rock, near Bayard, Nebraska, USA) 9 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Chimney Rock - an erosional pinnacle near the town of Bayard, Nebraska, USA.The chimney itself is composed of relatively hard, weathering-resistant sandstones of the Miocene-to-Oligocene-aged Arikaree Group (Monroe Creek-Harrison Formation over Gering Formation). The sloping cone below the pinnacle is composed of relatively soft "clays" of the Brule Formation (Oligocene).Two whitish-gray volcanic ash beds are present in the stratigraphic section of Chimney Rock. Studies have indicated that the source volcano was to the west of here.Chimney Rock is an erosional remnant of a moderately extensive range of hills called Wildcat Ridge, or Wildcat Hills. The bedrock in this part of Nebraska is relatively young - Tertiary in age. Before the Pliocene, sedimentation was occurring in this area. Since then, erosion has been dominant. Chimney Rock is one of several distinctively eroded features in the Wildcat Ridge area - others include Courthouse Rock, Jail Rock, and Scott's Bluff. (www.flickr.com/photos/fromdan/7959086200 and www.flickr.com/photos/courthouselover/15278743477)Chimney Rock's pinnacle was much taller in historical times. It has been reduced in size and damaged by a combination of natural processes and human vandalism. Natural erosion, lightning, and target practice by gun nerds and airplanes have significantly damaged this feature.Locality: Chimney Rock, northern side of Wildcat Ridge (Wildcat Hills), south of the North Platte River, off Chimney Rock Road, south-southwest of the town of Bayard, western Morrill County, western Nebraska, USA (41° 42' 13.87" North latitude, 103° 20' 52.71" West longitude) |
| 撮影日 | 2012-08-01 15:09:23 |
| 撮影者 | James St. John |
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