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In areas of low uplift rate on the Pacific Coast of North America, reoccupation of emergent marine terraces by later high-sea stands has been hypothesized to explain the existence of thermally anomalous faunas (mixtures of warm and cool species) of last interglacial age. If uplift rates have been low for much of the Quaternary, it follows that higher (older) terraces should also show evidence of reoccupation. Strontium isotope analyses of fossils from a high-elevation marine terrace on Anacapa Island, California yield a suite of ages ranging from ~2.4-2.3 Ma to ~1.4-1.5 Ma. These results indicate that terrace reoccupation and fossil mixing on Anacapa Island could have taken place over several interglacial periods...
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This release of digital geologic map data covers the Niobrara National Scenic River, a 76-mile stretch of river at the northern edge of the Nebraska Sand Hills. The mapped area includes the National Park Service unit of the Niobrara National Scenic River and the adjoining Middle Niobrara Preserve of The Nature Conservancy, and the Fort Niobrara Wildlife Refuge of the U.S. Fish and Wildlife Service. These digital geologic map data focus on the surficial geologic framework, dominated by the late Quaternary geology, of the Niobrara River valley corridor. These data are the result of geologic mapping begun by the U.S. Geological Survey in 2011 and continuing for about a decade. Mapping is based on geomorphic and other...
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This data release presents geologic map data for the surficial geology of the Aztec 1-degree by 2-degree quadrangle. The map area lies within two physiographic provinces of Fenneman (1928): the Southern Rocky Mountains province, and the Colorado Plateau province, Navajo section. Geologic mapping is mostly compiled from published geologic map data sources ranging from 1:24,000 to 1:250,000 scale, with limited new interpretive contributions. Gaps in map compilation are related to a lack of published geologic mapping at the time of compilation, and not necessarily a lack of surficial deposits. Much of the geology incorporated from published geologic maps is adjusted based on digital elevation model and natural-color...


    map background search result map search result map Strontium isotope, amino acid, and fossil taxonomy data to aid in identifying instances of marine terrace reoccupation on Anacapa and San Miguel Islands, California, USA Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map Geologic Map of the valley corridor of the Niobrara National Scenic River, Nebraska Strontium isotope, amino acid, and fossil taxonomy data to aid in identifying instances of marine terrace reoccupation on Anacapa and San Miguel Islands, California, USA Geologic Map of the valley corridor of the Niobrara National Scenic River, Nebraska Surficial geologic map database of the Aztec 1-degree by 2-degree quadrangle, northern New Mexico and southern Colorado: Contributions to the National Geologic Map