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Title: Timing of cut-and-fill sequences in the John Day Formation (Eocene-Oligocene), Painted Hills area, central Oregon

Abstract

Large-scale cut-and-fill features in the Eocene-Oligocene part of the John Day Formation in the Pained Hills area of central Oregon can be interpreted as terrestrial depositional sequences, mapped as lithostratigraphic units, and correlated to North American Land Mammal Ages (NALMA). New laser-fusion 40Ar/39Ar single-crystal ages from the John Day Formation provide evidence for the timing of these sequences and a revised placement of the Eocene-Oligocene boundary. The sequences are bound by erosional surfaces that have relief of up to 60 m, are marked in places by claystone breccias full of reworked soil clasts, and separate otherwise conformable strata. The lowermost depositional sequence in the John Day Formation contains very well developed, Fe- and Al-rich paleosols, laterite horizons, and the welded tuff of member A (39.7 my), and probably correlates to the Duchesean and Chadronian NALMA. These brick-rid claystones are sharply truncated by prominent detrital laterite horizon. Overlying this basal sequence is a second sequence of much less well developed paleosols, abundant tuffs and lacustrine tuffaceous claystones. This sequence contains a distinctive biotite tuff (33 my) and the type locality of the Bridge Creek fossil flora and probably correlates to the Orellan NALMA. Above this biotite tuff are alternating red, darkmore » gray, and tan paleosols and a prominent crystal vitric tuff (32.7 my). The Eocene-Oligocene boundary lies between these two sequences, associated with the laterite horizon that truncates the basal red beds. A major truncation surface cuts this sequence and is overlain by a third sequence of thin red paleosols which probably correlates with the Whitneyan NALMA. Above this is a fourth sequence (Arikareean NALMA) consisting of greenish-tan paleosols, a crystal vitric tuff near its base (29.8 my) and the Picture Gorge Ignimbrite (28.7 my).« less

Authors:
;  [1];  [2];  [3]
  1. Univ. of Oregon, Eugene, OR (United States). Dept. of Geological Sciences
  2. Inst. of Human Origins, Berkeley, CA (United States)
  3. John Day Fossil Beds National Monument, John Day, OR (United States)
Publication Date:
OSTI Identifier:
5422951
Report Number(s):
CONF-9305259-
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; GEOLOGIC FORMATIONS; ISOTOPE DATING; STRATIGRAPHY; OREGON; SEDIMENTARY ROCKS; ARGON 39; ARGON 40; DEPOSITION; GEOLOGIC STRATA; SOILS; TERTIARY PERIOD; TUFF; AGE ESTIMATION; ARGON ISOTOPES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; CENOZOIC ERA; DEVELOPED COUNTRIES; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; GEOLOGIC AGES; GEOLOGIC STRUCTURES; GEOLOGY; ISOTOPES; LIGHT NUCLEI; NORTH AMERICA; NUCLEI; RADIOISOTOPES; ROCKS; STABLE ISOTOPES; USA; YEARS LIVING RADIOISOTOPES; 580000* - Geosciences

Citation Formats

Bestland, E A, Retallack, G J, Swisher, III, C C, and Fremd, T J. Timing of cut-and-fill sequences in the John Day Formation (Eocene-Oligocene), Painted Hills area, central Oregon. United States: N. p., 1993. Web.
Bestland, E A, Retallack, G J, Swisher, III, C C, & Fremd, T J. Timing of cut-and-fill sequences in the John Day Formation (Eocene-Oligocene), Painted Hills area, central Oregon. United States.
Bestland, E A, Retallack, G J, Swisher, III, C C, and Fremd, T J. 1993. "Timing of cut-and-fill sequences in the John Day Formation (Eocene-Oligocene), Painted Hills area, central Oregon". United States.
@article{osti_5422951,
title = {Timing of cut-and-fill sequences in the John Day Formation (Eocene-Oligocene), Painted Hills area, central Oregon},
author = {Bestland, E A and Retallack, G J and Swisher, III, C C and Fremd, T J},
abstractNote = {Large-scale cut-and-fill features in the Eocene-Oligocene part of the John Day Formation in the Pained Hills area of central Oregon can be interpreted as terrestrial depositional sequences, mapped as lithostratigraphic units, and correlated to North American Land Mammal Ages (NALMA). New laser-fusion 40Ar/39Ar single-crystal ages from the John Day Formation provide evidence for the timing of these sequences and a revised placement of the Eocene-Oligocene boundary. The sequences are bound by erosional surfaces that have relief of up to 60 m, are marked in places by claystone breccias full of reworked soil clasts, and separate otherwise conformable strata. The lowermost depositional sequence in the John Day Formation contains very well developed, Fe- and Al-rich paleosols, laterite horizons, and the welded tuff of member A (39.7 my), and probably correlates to the Duchesean and Chadronian NALMA. These brick-rid claystones are sharply truncated by prominent detrital laterite horizon. Overlying this basal sequence is a second sequence of much less well developed paleosols, abundant tuffs and lacustrine tuffaceous claystones. This sequence contains a distinctive biotite tuff (33 my) and the type locality of the Bridge Creek fossil flora and probably correlates to the Orellan NALMA. Above this biotite tuff are alternating red, dark gray, and tan paleosols and a prominent crystal vitric tuff (32.7 my). The Eocene-Oligocene boundary lies between these two sequences, associated with the laterite horizon that truncates the basal red beds. A major truncation surface cuts this sequence and is overlain by a third sequence of thin red paleosols which probably correlates with the Whitneyan NALMA. Above this is a fourth sequence (Arikareean NALMA) consisting of greenish-tan paleosols, a crystal vitric tuff near its base (29.8 my) and the Picture Gorge Ignimbrite (28.7 my).},
doi = {},
url = {https://www.osti.gov/biblio/5422951}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 25:5,
place = {United States},
year = {Thu Apr 01 00:00:00 EST 1993},
month = {Thu Apr 01 00:00:00 EST 1993}
}

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