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Oreodont Tuff

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Journal Article
Journal: GSA Bulletin
Published: 01 April 1990
GSA Bulletin (1990) 102 (4): 459–477.
... beds on the east. Facies distribution and sparse paleocurrent data suggest that the conglomeratic sequence was derived from sources to the south and southwest and that the finergrained beds were deposited in the more distal part of the basin to the east and northeast. The Oreodont Tuff, situated about...
Journal Article
Journal: GSA Bulletin
Published: 01 April 1990
GSA Bulletin (1990) 102 (4): 478–493.
... conventional 40 K- 40 Ar and 40 Ar/ 39 Ar single-crystal laser-fusion methods. Multiple analyses on minerals from 5 superposed tuffs yielded the following mean 40 K- 40 Ar ages: Rak Tuff at 16.3 ± 0.3 m.y., Oreodont Tuff at 15.9 ± 0.2 m.y., Dated Tuff at 14.8 ± 0.2 m.y., Hemicyon Tuff at 14.0 ± 0.1 m.y...
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Figure 2. Schematic stratigraphic sections. All age uncertainties are shown as 2σ. (A) The composite section of Woodburne (1996) compiled from the 40Ar/39Ar and K-Ar ages of smaller dated sections in MacFadden et al. (1990). See Table 1 for description of ages. The Skyline Tuff is in bold because it is an important marker bed for basinwide correlation. The underscored ages for the Oreodont and Valley View Tuffs are considered the most robust because they are 40Ar/39Ar ages of sanidines. (B) Carnivore Canyon section and preferred age of the Hemicyon Tuff (MacFadden et al., 1990). (C) Hell Gate Basin section and preferred age of the Lapilli Sandstone (MacFadden et al., 1990). (D) Steep-side Quarry section from Coon Canyon and preferred age of the Oreodont Tuff (MacFadden et al., 1990). (E) Rainbow Basin section and preferred ages of the Red, Rak, and Dated Tuffs (MacFadden et al., 1990). The (diagenetic) age of the Skyline Tuff is from this section as well (WoldeGabriel et al., 1996). (F) Our measured section from the south limb of the syncline in Owl Canyon. Tufas are exposed on a ridge southwest of Owl Canyon Campground (loc. 1, Fig. 1). This locality is 260 m below the Skyline Tuff and is marked with a star. U-Pb ages for three tufas in italics. (G) The section between Owl and Solomon Canyons is the lithostratigraphic type section for the Barstow Formation and was measured on the north limb of the Barstow syncline (Durrell, 1953). The position of the phytoherm tufa locality (sample OCE-1) on the north limb of the syncline is estimated on this section with a star (loc. 2, Fig. 1). U-Pb tufa age in italics. The stratigraphic position of the final tufa locality (loc. 3, Fig. 1) cannot be estimated on these sections because its current location is covered by Quaternary alluvium
Published: 01 March 2005
because it is an important marker bed for basinwide correlation. The underscored ages for the Oreodont and Valley View Tuffs are considered the most robust because they are 40 Ar/ 39 Ar ages of sanidines. (B) Carnivore Canyon section and preferred age of the Hemicyon Tuff ( MacFadden et al., 1990 ). (C
Series: GSA Special Papers
Published: 01 January 1990
DOI: 10.1130/SPE244-p69
... that blanketed both valleys and interchannel reaches. Fluvial sediments within the valleys include much spatially dispersed mammal bone that had been scavenged and subaerially weathered prior to burial. Waterholes, situated in or adjacent to the valleys, filled with tuff and carbonate mud containing freshwater...
Journal Article
Journal: GSA Bulletin
Published: 01 March 2005
GSA Bulletin (2005) 117 (3-4): 276–287.
... because it is an important marker bed for basinwide correlation. The underscored ages for the Oreodont and Valley View Tuffs are considered the most robust because they are 40 Ar/ 39 Ar ages of sanidines. (B) Carnivore Canyon section and preferred age of the Hemicyon Tuff ( MacFadden et al., 1990 ). (C...
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Journal Article
Published: 01 May 2008
The Journal of Geology (2008) 116 (3): 211–237.
... volcanic tuffs for our correlation with the geomagnetic polarity timescale. Many of the rocks analyzed showed unusual magnetic behavior, possibly due to the known zeolitization in this region, thereby precluding an abundance of class 1 polarity determinations. Nevertheless, preliminary results indicate...
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Journal Article
Published: 20 March 2014
The Journal of Geology (2014) 122 (2): 113–135.
... of the lower limit of the Centenario Fauna to no younger than ∼19 Ma, but the upper limit has remained problematical. A fresh exposure of the Cucaracha tuff, a prominent marker horizon within our measured sections, has yielded two new radioisotopic determinations: (1) an 40 Ar/ 39 Ar age of 18.96 ± 0.90 Ma...
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Journal Article
Journal: AAPG Bulletin
Published: 01 August 1956
AAPG Bulletin (1956) 40 (8): 1899–1914.
... pyroclastic conglomerate, tuff, sandstone, and claystone of middle Miocene age, unconformably overlying all older rocks and unconformably overlain by rocks of middle Pliocene age. The name Teewinot formation is used for 5,000 feet or more of white limestone, pumicite, tuff, claystone, diatomite...
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Journal Article
Published: 01 July 2010
Journal of the Geological Society (2010) 167 (4): 817–825.
... provided a basis for geochronology ( Woodburne et al . 1990 ). The base of the ‘Middle' Member is locally defined by the Rak Tuff (16.3 ± 0.3 Ma). The concretions that bear ostracodes with soft tissues occur 62.5 m above the Rak Tuff, and approximately halfway between it and the Oreodont Tuff (15.8 ± 0.3...
FIGURES
Journal Article
Published: 01 May 2009
Journal of Paleontology (2009) 83 (3): 489–492.
... section; also above a prominent welded tuff and below the contact with the Pedro Miguel volcanics; middle Miocene, probably either Hemingfordian or early Barstovian North American Land Mammal Age (He1 through Ba1, sensu Tedford et al., 2004 ), ca. 18 to 15 million years ago. UF 236937 preserves...
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Journal Article
Journal: Paleobiology
Published: 01 January 2004
Paleobiology (2004) 30 (4): 561–588.
... and possums. The particular tooth emphasis morphospace chosen here works best for primates, carnivores, mustelids, and primitive ungulates. In tooth emphasis the gracile oreodont ( Eporeodon occidentalis ) is not significantly different from the robust oreodont ( Merycochoerus superbus ). Both taxa...
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Journal Article
Journal: Geology
Published: 01 April 2004
Geology (2004) 32 (4): 297–300.
..., Washington, was 21 ± 5 cm (uncompacted). Among 358 Oligocene paleosols observed near Kimberly, Oregon, between the 28.7 Ma John Day Tuff H and the 23.6 Ma uppermost Kimberly Member, there are 105 cycles ( Fig. 2A ). Most of the Oligocene paleoclimatic cycles represent Milankovitch-obliquity cycles (41 k.y...
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Journal Article
Journal: PALAIOS
Published: 30 April 2020
PALAIOS (2020) 35 (4): 175–190.
... dated through biostratigraphy ( Woodburne et al. 1990 ; Pagnac 2009 ), magnetostratigraphy ( MacFadden et al. 1990 ; Woodburne 1996 ), and radiometric dating of airfall tuffs ( Woodburne et al. 1990 ; Miller et al. 2010 ; Miller et al. 2013 ). In the Mud Hills, the Barstow Formation ranges in age...
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Journal Article
Published: 01 May 2007
The Journal of Geology (2007) 115 (3): 271–294.
... and representative of Eocene to Holocene and the need for sites not so geographically dispersed as to sample different local climates. The greatest temporal resolution was found in Oregon ( fig. 2 A ), which has a sequence of tuffs and lavas much thicker than those of Montana and Nebraska. The Montana sequence...
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Journal Article
Journal: Geology
Published: 03 January 2020
Geology (2020) 48 (3): 273–277.
...) and SDP (33.41 ± 0.04 Ma) ( Sahy et al., 2015 ), and in the Orellan stage based on the first occurrences of oreodonts Miniochoerus affinis and Miniochoerus gracilis , and rodent Eumys elegans ( Zanazzi et al., 2009 ; Sahy et al., 2015 ). It is highly unlikely that this younging trend was caused...
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Journal Article
Published: 01 June 2021
Rocky Mountain Geology (2021) 56 (1): 37–50.
..., conglomerate, and shale alternating with layers of tuff derived from the Mount Aetna caldera ( Johnson, 1937 ; Stark et al., 1949 ; McIntosh and Chapin, 2004 ). The sedimentary facies are interpreted as lacustrine and fluvial paleoenvironments deposited in and near ancient Lake Antero, a large freshwater...
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Series: GSA Memoirs
Published: 27 September 2021
DOI: 10.1130/2021.1217(15)
EISBN: 9780813782171
... the base of the Lower Orinda Formation at Highway 24 to be older than 11.5 Ma. This is consistent with the age derived from the 11.5 Ma Cull Canyon Tuff. The oreodont lower P1 (UCMP 218443, V12012) is a little smaller than examples from large individuals of Merychyus major found in both the Dove...
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Journal Article
Published: 01 March 2010
Journal of Paleontology (2010) 84 (2): 288–298.
... part of the Cucaracha Formation, which is stratigraphically below the welded tuff marker bed ( Fig. 2 ). The middle part of the Cucaracha Formation remains undated, except for the other land mammal fossils. Taking these constraints, the Centenario Fauna (and the Gaillard Cut L.F. included as part...
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Journal Article
Published: 01 May 2023
Journal of Paleontology (2023) 97 (3): 735–753.
... lacustrine and brackish estuarine deposits (Wagner et al., 2021 ). Figure 1. Generalized stratigraphic sections with radioisotopic dated tuffs of the Contra Costa Group ( 1 ) in the East San Francisco Bay area, California, and ( 2 ) the Warm Springs area, Oregon, showing the relative positions...
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Journal Article
Published: 01 March 2002
The Journal of Geology (2002) 110 (2): 123–140.
... by the Clarendonian chronofauna was followed by a decline of ungulate diversity such that the number of genera at 2 Ma was about one-third that at 15 Ma (Janis et al. 2000 ). Characteristic mammalian lineages disappeared from the Great Plains, including the oreodonts, chalicotheres, and rhinos, and elements...
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