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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Vermes
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Carlile Shale (5)
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Primary terms
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carbon
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Cenozoic
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Quaternary
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Tertiary
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Cypress Hills Formation (1)
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lower Tertiary (1)
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Ogallala Formation (1)
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Paleogene
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lower Eocene (1)
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Paleocene
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lower Paleocene
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K-T boundary (3)
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Ravenscrag Formation (1)
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Chordata
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Invertebrata
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Echinodermata
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Crinozoa
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Mollusca
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Bivalvia
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Veneroida
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Pterioida
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Cephalopoda
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Gastropoda (5)
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Protista
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Foraminifera
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-
-
-
-
Globigerinacea (1)
-
-
-
Radiolaria (3)
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Vermes
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Annelida (1)
-
-
-
isotopes
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stable isotopes
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B-11/B-10 (1)
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C-13/C-12 (13)
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O-18/O-16 (11)
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land use (1)
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Mesozoic
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Cretaceous
-
Colorado Group (1)
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Dakota Formation (1)
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Graneros Shale (3)
-
Lower Cretaceous
-
Mowry Shale (2)
-
Muddy Sandstone (1)
-
-
Mancos Shale (1)
-
Upper Cretaceous
-
Bearpaw Formation (5)
-
Belle Fourche Shale (1)
-
Campanian
-
lower Campanian (2)
-
upper Campanian (8)
-
-
Carlile Shale (5)
-
Codell Sandstone Member (3)
-
Coniacian (1)
-
Fort Hays Limestone Member (2)
-
Fox Hills Formation (5)
-
Gammon Ferruginous Member (3)
-
Greenhorn Limestone (5)
-
Hell Creek Formation (1)
-
Judith River Formation (1)
-
K-T boundary (3)
-
Lance Formation (1)
-
Laramie Formation (2)
-
Lewis Shale (1)
-
Maestrichtian (9)
-
Montana Group (2)
-
Niobrara Formation (20)
-
Parkman Sandstone (1)
-
Pierre Shale (127)
-
Senonian (30)
-
Shannon Sandstone Member (1)
-
Sharon Springs Member (8)
-
Smoky Hill Chalk Member (1)
-
Sussex Sandstone Member (1)
-
Turonian
-
upper Turonian (1)
-
-
Two Medicine Formation (1)
-
-
-
Jurassic
-
Posidonia Shale (1)
-
-
-
metals
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actinides
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uranium (2)
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alkali metals
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sodium (1)
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alkaline earth metals
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strontium
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platinum group
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Rocky Mountains
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Western Interior
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Western Interior Seaway (23)
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ocean circulation (1)
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O-18/O-16 (11)
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paleontology (17)
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Paleozoic
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Barnett Shale (1)
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-
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Devonian
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Middle Devonian
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Prairie Evaporite (1)
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-
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Permian
-
Lyons Sandstone (1)
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upper Paleozoic
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Fountain Formation (1)
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palynomorphs
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Dinoflagellata (3)
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megaspores (1)
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miospores (1)
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petroleum
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natural gas (7)
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shale oil (1)
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petrology (1)
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Plantae
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United States
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California
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Pierre Shale
Electrical Resistivity Imaging of Recent Landslides in Colorado Springs, Colorado, USA
ABSTRACT Detrital zircon U-Pb and (U-Th)/He ages from latest Cretaceous–Eocene strata of the Denver Basin provide novel insights into evolving sediment sourcing, recycling, and dispersal patterns during deposition in an intracontinental foreland basin. In total, 2464 U-Pb and 78 (U-Th)/He analyses of detrital zircons from 21 sandstone samples are presented from outcrop and drill core in the proximal and distal portions of the Denver Basin. Upper Cretaceous samples that predate uplift of the southern Front Range during the Laramide orogeny (Pierre Shale, Fox Hills Sandstone, and Laramie Formation) contain prominent Late Cretaceous (84–77 Ma), Jurassic (169–163 Ma), and Proterozoic (1.69–1.68 Ga) U-Pb ages, along with less abundant Paleozoic through Archean zircon grain ages. These grain ages are consistent with sources in the western U.S. Cordillera, including the Mesozoic Cordilleran magmatic arc and Yavapai-Mazatzal basement, with lesser contributions of Grenville and Appalachian zircon recycled from older sedimentary sequences. Mesozoic zircon (U-Th)/He ages confirm Cordilleran sources and/or recycling from the Sevier orogenic hinterland. Five of the 11 samples from syn-Laramide basin fill (latest Cretaceous–Paleocene D1 Sequence) and all five samples from the overlying Eocene D2 Sequence are dominated by 1.1–1.05 Ga zircon ages that are interpreted to reflect local derivation from the ca. 1.1 Ga Pikes Peak batholith. Corresponding late Mesoproterozoic to early Neoproterozoic zircon (U-Th)/He ages are consistent with local sourcing from the southern Front Range that underwent limited Mesozoic–Cenozoic unroofing. The other six samples from the D1 Sequence yielded detrital zircon U-Pb ages similar to pre-Laramide units, with major U-Pb age peaks at ca. 1.7 and 1.4 Ga but lacking the 1.1 Ga age peak found in the other syn-Laramide samples. One of these samples yielded abundant Mesozoic and Paleozoic (U-Th)/He ages, including prominent Early and Late Cretaceous peaks. We propose that fill of the Denver Basin represents the interplay between locally derived sediment delivered by transverse drainages that emanated from the southern Front Range and a previously unrecognized, possibly extraregional, axial-fluvial system. Transverse alluvial-fluvial fans, preserved in proximal basin fill, record progressive unroofing of southern Front Range basement during D1 and D2 Sequence deposition. Deposits of the upper and lower D1 Sequence across the basin were derived from these fans that emanated from the southern Front Range. However, the finer-grained, middle portion of the D1 Sequence that spans the Cretaceous-Paleogene boundary was deposited by both transverse (proximal basin fill) and axial (distal basin fill) fluvial systems that exhibit contrasting provenance signatures. Although both tectonic and climatic controls likely influenced the stratigraphic development of the Denver Basin, the migration of locally derived fans toward and then away from the thrust front suggests that uplift of the southern Front Range may have peaked at approximately the Cretaceous-Paleogene boundary.