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Journal Article

Paleoclimatic inferences from paleopedology and magnetism of the Permian Maroon Formation loessite, Colorado, USA

Kristy L. Tramp, G.S. (Lynn) Soreghan, R. Douglas Elmore
Journal: GSA Bulletin
Published: 01 May 2004
GSA Bulletin (2004) 116 (5-6): 671–686.
DOI: https://doi.org/10.1130/B25354.1
.... Additionally, magnetic susceptibility aids assessment of the intensity of pedogenesis. Bulk magnetic susceptibility (χ b ) through the section repeatedly fluctuates between low values (average 3.51 × 10 −8 ± 1.59 × 10 −8 m 3 /kg) in parent loessite and higher values (average 5.70 × 10 −8 ± 2.70 × 10 −8 m 3 /kg...
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View PDF for article title, Paleoclimatic inferences from paleopedology and magnetism of the Permian Maroon Formation <span class="search-highlight">loessite</span>, Colorado, USA
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Journal Article

Sedimentologic-magnetic record of western Pangean climate in upper Paleozoic loessite (lower Cutler beds, Utah)

G.S. (Lynn) Soreghan, R. Douglas Elmore, Michael T. Lewchuk
Journal: GSA Bulletin
Published: 01 August 2002
GSA Bulletin (2002) 114 (8): 1019–1035.
DOI: https://doi.org/10.1130/0016-7606(2002)114<1019:SMROWP>2.0.CO;2
... Pangea. The lower Cutler beds consist of ∼250 m of lithified eolian silt (loessite) and marine-reworked and fluvially reworked loessite, with abundant intercalated paleosols comprising Protosols, Argillisols, and Calcisols. The evolution from loessite and marine-reworked loessite with abundant Calcisols...
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View PDF for article title, Sedimentologic-magnetic record of western Pangean climate in upper Paleozoic <span class="search-highlight">loessite</span> (lower Cutler beds, Utah)
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Journal Article

Paleowinds inferred from detrital-zircon geochronology of upper Paleozoic loessite, western equatorial Pangea

Michael J. Soreghan, G.S. (Lynn) Soreghan, Michael A. Hamilton
Journal: Geology
Published: 01 August 2002
Geology (2002) 30 (8): 695–698.
DOI: https://doi.org/10.1130/0091-7613(2002)030<0695:PIFDZG>2.0.CO;2
...Michael J. Soreghan; G.S. (Lynn) Soreghan; Michael A. Hamilton Abstract U-Pb geochronology of detrital zircons from upper Paleozoic loessite (western United States) provides data bearing on atmospheric circulation within western equatorial Pangea. Zircon age spectra of four loessites from three...
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View PDF for article title, Paleowinds inferred from detrital-zircon geochronology of upper Paleozoic <span class="search-highlight">loessite</span>, western equatorial Pangea
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Journal Article

Equatorial Aridity in Western Pangea: Lower Permian Loessite and Dolomitic Paleosols in Northeastern New Mexico, U.S.A.

Jennifer L.P. Kessler, Gerilyn S. Soreghan, Herbert J. Wacker
Published: 01 September 2001
Journal of Sedimentary Research (2001) 71 (5): 817–832.
DOI: https://doi.org/10.1306/2DC4096B-0E47-11D7-8643000102C1865D
... and volumetrically significant eolian silt (loessite). Fluvial facies dominate the lower half of the study interval and include matrix-supported, massive conglomeratic debris-flow units and laminated arkosic sandstone, whereas loessite dominates the upper half of the study section and consists of massive, well...
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View PDF for article title, Equatorial Aridity in Western Pangea: Lower Permian <span class="search-highlight">Loessite</span> and Dolomitic Paleosols in Northeastern New Mexico, U.S.A.
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Journal Article

Triassic loessite of north-central Utah; stratigraphy, petrophysical character, and paleoclimate implications

Marjorie A. Chan
Published: 01 March 1999
Journal of Sedimentary Research (1999) 69 (2): 477–485.
DOI: https://doi.org/10.2110/jsr.69.477
...Marjorie A. Chan Abstract Even though paleoloess (loessite) deposits serve as important stratigraphic markers and can imply specific environmental and/or climatic conditions, few have been described in detail. The Mahogany Member of the Triassic Ankareh Formation of north-central Utah contains...
View PDF for article title, Triassic <span class="search-highlight">loessite</span> of north-central Utah; stratigraphy, petrophysical character, and paleoclimate implications
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Journal Article

Pedogenically enhanced magnetic susceptibility variations preserved in Paleozoic loessite

G. S. Soreghan, R. D. Elmore, B. Katz, M. Cogoini, S. Banerjee
Journal: Geology
Published: 01 November 1997
Geology (1997) 25 (11): 1003–1006.
DOI: https://doi.org/10.1130/0091-7613(1997)025<1003:PEMSVP>2.3.CO;2
..., however, magnetic studies of loess sequences have been applied exclusively to Quaternary deposits. Here we demonstrate preservation of magnetic susceptibility variations in an upper Paleozoic loessite sequence of western North America. Magnetic susceptibility through a continuously exposed test section...
View PDF for article title, Pedogenically enhanced magnetic susceptibility variations preserved in Paleozoic <span class="search-highlight">loessite</span>
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Journal Article

Significance of loessite in the Maroon Formation (Middle Pennsylvanian to Lower Permian), Eagle Basin, Northwest Colorado

Samuel Y. Johnson
Published: 01 September 1989
Journal of Sedimentary Research (1989) 59 (5): 782–791.
DOI: https://doi.org/10.1306/212F9070-2B24-11D7-8648000102C1865D
... interpreted as loessite (lithified loess) along its downwind basin margin. The section of inferred loessite in the Maroon Formation is locally at least 490 m thick and consists in large part of structureless and nearly structureless beds of homogeneous sandy siltstone. Bed contacts are generally planar...
View PDF for article title, Significance of <span class="search-highlight">loessite</span> in the Maroon Formation (Middle Pennsylvanian to Lower Permian), Eagle Basin, Northwest Colorado
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Journal Article

Late Precambrian glacial loessites from North Norway and Svalbard

M. B. Edwards
Published: 01 March 1979
Journal of Sedimentary Research (1979) 49 (1): 85–91.
DOI: https://doi.org/10.1306/212F76C6-2B24-11D7-8648000102C1865D
...M. B. Edwards Abstract Faintly stratified siltstones intercalated with late Precambrian tillites and glaciolacustrine and glaciomarine mudstones are interpreted to be indurated wind deposited silts, or "loessites." In thin section, the siltstones are distinguished by their high silt and low clay...
View PDF for article title, Late Precambrian glacial <span class="search-highlight">loessites</span> from North Norway and Svalbard
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A) Erosional top of Facies D1 with large clasts of loessite (dotted oval) in the overlying deposits, implying induration of the loessite before deposition of the Gething Formation. Vertical fabric in loessite is the result of rooting (arrow). From well 6-8-67-09W6, depth 2713.73 mKB, adjusted to well logs. B) Facies D1 overlain by coal (white arrow) with no seat earth. White bar for scale 5 cm long. From well 6-8-68-8W6, 2511.20 mKB, adjusted to well logs. C) Thin section of void-filling clay argillans (arrow) in conglomerate under crossed nichols. From well 5-30-66-10W6, 2879.79mKB, adjusted to well logs. D) Thin section with clay bridges and linings in Cadomin Formation sandstone. From well 10-29-66-6W6, 2502.94 mKB, adjusted to well logs. E) Thin section showing partial dissolution of chert grains (arrow). From well 10-8-70-9W6, 2193.50 mKB, adjusted to well logs.

A) Erosional top of Facies D1 with large clasts of loessite (dotted oval) ...

Published: 27 August 2019
Fig. 17.— A) Erosional top of Facies D1 with large clasts of loessite (dotted oval) in the overlying deposits, implying induration of the loessite before deposition of the Gething Formation. Vertical fabric in loessite is the result of rooting (arrow). From well 6-8-67-09W6, depth 2713.73 mKB
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Plot of alteration depth (as measured downward from the top of the loessite that caps the Cadomin Formation) versus distance between the top-Bluesky Formation datum and the top of the Cadomin Formation, which is an inverse proxy for depositional elevation: smaller distances represent higher, older terrace levels. The line represents the best-fit regression line. See text for additional discussion of measurement methodology and the inferred significance of the anomalous outlying point (arrow).

Plot of alteration depth (as measured downward from the top of the loessite...

Published: 27 August 2019
Fig. 18.— Plot of alteration depth (as measured downward from the top of the loessite that caps the Cadomin Formation) versus distance between the top-Bluesky Formation datum and the top of the Cadomin Formation, which is an inverse proxy for depositional elevation: smaller distances represent
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Figure 3. Outcrop photographs of Maroon Formation loessite and photomicrographs of loessite and paleosol microfabrics. (A) View of vertical section of Maroon Formation loessite and interbedded paleosols (dark bands denoted with arrows). (B) Section fifteen meter thick section of interbedded loessite and paleosols (denoted by arrows) of study section. (C) Typical loessite fabric. Width of field of view represents 1.44 mm; cross-polarized light. (D) Loessite grains with dust rims that are commonly thicker in grain indentations. Width represents 0.72 mm; plane-polarized light. (E) Outcrop view of weakly developed paleosol (Protosol) denoted with P. Image height represents ∼1.5 m. (F) Disseminated dolomite cement in a carbonate-rich zone. Width represents 0.72 mm; cross-polarized light. (G) Protosol clay-rich zone where clay infills cracks, but does not constitute an appreciable amount of the fabric. Width represents 1.44 mm; plane-polarized light. (H) Disseminated dolomite cement in carbonate-rich zone in an Argillisol. Width represents 0.72 mm; cross- polarized light. (Caption continued on p. 677.)

Figure 3. Outcrop photographs of Maroon Formation loessite and photomicrogr...

Published: 01 May 2004
Figure 3. Outcrop photographs of Maroon Formation loessite and photomicrographs of loessite and paleosol microfabrics. (A) View of vertical section of Maroon Formation loessite and interbedded paleosols (dark bands denoted with arrows). (B) Section fifteen meter thick section of interbedded
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TABLE 1. AVERAGE MODAL AND GEOCHEMICAL COMPOSITION OF PARENT LOESSITE, LOWE...

Published: 01 August 2002
TABLE 1. AVERAGE MODAL AND GEOCHEMICAL COMPOSITION OF PARENT LOESSITE, LOWER CUTLER BEDS, UTAH
Journal Article

Abrupt and high-magnitude changes in atmospheric circulation recorded in the Permian Maroon Formation, tropical Pangaea

M.J. Soreghan, N. Heavens, G.S. Soreghan, P.K. Link, M.A. Hamilton
Journal: GSA Bulletin
Published: 01 March 2014
GSA Bulletin (2014) 126 (3-4): 569–584.
DOI: https://doi.org/10.1130/B30840.1
...M.J. Soreghan; N. Heavens; G.S. Soreghan; P.K. Link; M.A. Hamilton Abstract Geochemical, magnetic, sedimentologic, and U-Pb detrital zircon data from loessite-paleosol couplets within the Maroon Formation of Colorado (western U.S.) record abrupt and high-magnitude changes in atmospheric circulation...
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Cumulative probability plots of U-Pb ages from detrital zircons of four loessite-paleosol pairs in the Maroon Formation. Two loessite-paleosol pairs are from the study interval (M203.4–M203.8 and M210–M211.7), whereas one loessite-paleosol pair is from ∼100 m below the study interval (M120–M121P) and one loessite-paleosol pair is from ∼150 m above the study interval (UR364–UR364p). The area under each curve represents the summed Gaussian distribution of individual ages and associated errors for each grain (see methods section for filtering criteria). Colored bands within each plot represent some of the age populations discussed in text: Y—young/volcanic grain (&lt;300 Ma) ages; EP—early Paleozoic; NP—Neoproterozoic; GR—Mesoproterozoic/Grenville; YM—Paleoproterozoic/Yavapai-Mazatzal.

Cumulative probability plots of U-Pb ages from detrital zircons of four loe...

Published: 01 March 2014
Figure 7. Cumulative probability plots of U-Pb ages from detrital zircons of four loessite-paleosol pairs in the Maroon Formation. Two loessite-paleosol pairs are from the study interval (M203.4–M203.8 and M210–M211.7), whereas one loessite-paleosol pair is from ∼100 m below the study interval
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A: Relative percentage of genetically significant microtextures in the Unaweep diamictite (this study) compared to nonglacial fluvial and glacial till strata studied by Mahaney and Kalm (2000). See GSA Data Repository for methods and Table DR2 for data. B: Weight percent TiO2 versus Al2O3 for loessite and pedogenically modified loessite from Lower Permian loessite of Colorado (Maroon Formation) and New Mexico (Abo-Tubb unit). See text for discussion, the Data Repository for methods, and Table DR3 for data (see footnote 1).

A: Relative percentage of genetically significant microtextures in the Unaw...

Published: 01 August 2008
Al 2 O 3 for loessite and pedogenically modified loessite from Lower Permian loessite of Colorado (Maroon Formation) and New Mexico (Abo-Tubb unit). See text for discussion, the Data Repository for methods, and Table DR3 for data (see footnote 1).
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Figure 8. Thermal demagnetization patterns of low-temperature SIRM for loessitic and paleosol samples. The SIRM were acquired at 19 K. Diamonds—well-developed paleosol; squares—loessite. The slight drop at about 110–120 K in both curves is the Verwey transition.

Figure 8. Thermal demagnetization patterns of low-temperature SIRM for loes...

Published: 01 May 2004
Figure 8. Thermal demagnetization patterns of low-temperature SIRM for loessitic and paleosol samples. The SIRM were acquired at 19 K. Diamonds—well-developed paleosol; squares—loessite. The slight drop at about 110–120 K in both curves is the Verwey transition.
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Permo-Carboniferous loess(ite) in the Ancestral Rocky Mountains region. A, More than 700 m of the lower Permian Maroon Formation loessite of northeastern Colorado (see Johnson 1989; Tramp et al. 2004), to date the thickest loess(ite) documented from any geologic interval on Earth. B, The ∼250 m of loess and intercalated paleosols of the lower Cutler beds of southeastern Utah (correlative to the proximal Cutler Formation; see Murphy 1987; Soreghan et al. 2002a). C, The massive character of the Maroon Formation loessite. D, Loessite of the Pennsylvanian-Permian Naco Group, Arizona (see Soreghan et al. 2007a). Outcrop height is ∼5 m near center of photo.

Permo-Carboniferous loess(ite) in the Ancestral Rocky Mountains region. A ...

Published: 14 March 2014
Figure 8. Permo-Carboniferous loess(ite) in the Ancestral Rocky Mountains region. A , More than 700 m of the lower Permian Maroon Formation loessite of northeastern Colorado (see Johnson 1989 ; Tramp et al. 2004 ), to date the thickest loess(ite) documented from any geologic interval on Earth
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Principal component plot of first two components (PC1 and PC2) based on centered, log-transformed whole-rock and trace-element data. Filled circles—thick loessites; open circles—thick paleosols; filled squares—thin loessites; open squared—thin paleosols. Primary components and their loading for PC1 and PC2 are listed under each plot. Data were plotted in the software program CoDaPack (version 2.01.6).

Principal component plot of first two components (PC1 and PC2) based on cen...

Published: 01 March 2014
Figure 10. Principal component plot of first two components (PC1 and PC2) based on centered, log-transformed whole-rock and trace-element data. Filled circles—thick loessites; open circles—thick paleosols; filled squares—thin loessites; open squared—thin paleosols. Primary components
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Core photographs and photomicrographs of depositional facies. Coin (2 cm diameter) used for scale in all core photos (here and in Figure 8) is 15 cm long. A) Pebbly debris-flow facies. B) Sandy fluvial facies showing local ripples and scour surfaces. C) Massive siltstone (loessite). D) Photomicrograph of siltstone (loessite) in plane-polarized light (PPL); vertical field of view is 1.33 mm.

Core photographs and photomicrographs of depositional facies. Coin (2 cm di...

Published: 01 September 2001
(loessite). D) Photomicrograph of siltstone (loessite) in plane-polarized light (PPL); vertical field of view is 1.33 mm.
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Measured section showing sedimentologic character and sample locations. Sample symbols are as follows: open circles and filled circles—magnetic susceptibility samples where the open circles are classified as loessite samples and the gray circles classified as paleosol samples for statistical analysis; black circles—grain size samples; P/L—geochemical samples (P—paleosol sample, L—loessite sample); large squares—detrital zircon samples. CIA—chemical index of alteration. rb—red brown; dk—dark; org—orange.

Measured section showing sedimentologic character and sample locations. Sam...

Published: 01 March 2014
Figure 3. Measured section showing sedimentologic character and sample locations. Sample symbols are as follows: open circles and filled circles—magnetic susceptibility samples where the open circles are classified as loessite samples and the gray circles classified as paleosol samples