Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration
Siliciclastic strata of the Colorado Plateau attract attention for their striking red, green, bleached, and variegated colors that potentially record both early depositional and later diagenetic events. We investigated the proximal-most strata of the Paradox Basin, from their onlap contact with the...
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Frontiers Media S.A.
2023-11-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2023.1219966/full |
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| author | Desiree P. Hullaster Gerilyn S. Soreghan Ravi K. Kukkadapu Brock S. Dumont Kato T. Dee Andrew S. Elwood Madden |
| author_facet | Desiree P. Hullaster Gerilyn S. Soreghan Ravi K. Kukkadapu Brock S. Dumont Kato T. Dee Andrew S. Elwood Madden |
| author_sort | Desiree P. Hullaster |
| collection | DOAJ |
| description | Siliciclastic strata of the Colorado Plateau attract attention for their striking red, green, bleached, and variegated colors that potentially record both early depositional and later diagenetic events. We investigated the proximal-most strata of the Paradox Basin, from their onlap contact with the Precambrian basement of the Uncompahgre Plateau to the younger Cutler strata exposed within 10 km of the Uncompahgre Plateau to attempt to understand the significance of the striking colors that occur here. These strata preserve a complex geology associated with buried paleorelief and sediment-related permeability variations at a major basin-uplift interface. Strata exposed within ∼1.5 km of the onlap contact exhibit a pervasive drab color in contrast to the generally red colors that predominate farther from this front. In-between, strata commonly host variegated red/green/bleached intercalations. Thin-section petrography, SEM, XRD, Raman spectroscopy, Mössbauer spectroscopy, and whole-rock geochemistry of samples representing different color variations from demonstrate that water–rock interactions charged the rocks with Fe(II) that persists primarily in the phyllosilicate fraction. Color variations reflect grain-size differences that allowed the reduction of fluids from regional fault and basement/fill contacts to permeate coarser-grained Cutler sediments. Hematite and chlorite occur in both red and green sediments but are absent in the bleached sediments. Pervasive hematite in both red and green layers suggests that sediments were hematite-rich before later alteration. Chlorite and smectite are elevated in green samples and inversely correlated with biotite content. Green coloration is generally associated with 1) coarser grain sizes, 2) spatial association with basement contacts, 3) elevated smectite and/or chlorite, 4) less total Fe but greater Fe(II)/Fe(III) primarily in the phyllosilicate fraction, and 5) uranium enrichment. The bleached coloration reflects the removal of pigmentary Fe(III) oxide, while the green coloration is due to the removal of pigmentary hematite and the abundance of Fe(II)-bearing phyllosilicates. Abundant mixed-layer and swelling clays such as smectite, illite/smectite, and chlorite/smectite (including tosudite) dominate the mineralogy of the clay fraction. These results are consistent with other studies demonstrating fault-associated fluid alteration in the Paradox Basin region. However, the pervasive greening was not observed in many of these studies and appears to reflect the unique aspects of the paleovalley system and the importance of biotite alteration to Fe(II)-bearing phyllosilicates. |
| first_indexed | 2024-03-11T10:12:42Z |
| format | Article |
| id | doaj.art-4fe52a74066c4cf3a0cbf10788857076 |
| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-03-11T10:12:42Z |
| publishDate | 2023-11-01 |
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| spelling | doaj.art-4fe52a74066c4cf3a0cbf107888570762023-11-16T13:30:34ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632023-11-011110.3389/feart.2023.12199661219966Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alterationDesiree P. Hullaster0Gerilyn S. Soreghan1Ravi K. Kukkadapu2Brock S. Dumont3Kato T. Dee4Andrew S. Elwood Madden5School of Geosciences, University of Oklahoma, Norman, OK, United StatesSchool of Geosciences, University of Oklahoma, Norman, OK, United StatesEnvironmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, United StatesSchool of Geosciences, University of Oklahoma, Norman, OK, United StatesSchool of Geosciences, University of Oklahoma, Norman, OK, United StatesSchool of Geosciences, University of Oklahoma, Norman, OK, United StatesSiliciclastic strata of the Colorado Plateau attract attention for their striking red, green, bleached, and variegated colors that potentially record both early depositional and later diagenetic events. We investigated the proximal-most strata of the Paradox Basin, from their onlap contact with the Precambrian basement of the Uncompahgre Plateau to the younger Cutler strata exposed within 10 km of the Uncompahgre Plateau to attempt to understand the significance of the striking colors that occur here. These strata preserve a complex geology associated with buried paleorelief and sediment-related permeability variations at a major basin-uplift interface. Strata exposed within ∼1.5 km of the onlap contact exhibit a pervasive drab color in contrast to the generally red colors that predominate farther from this front. In-between, strata commonly host variegated red/green/bleached intercalations. Thin-section petrography, SEM, XRD, Raman spectroscopy, Mössbauer spectroscopy, and whole-rock geochemistry of samples representing different color variations from demonstrate that water–rock interactions charged the rocks with Fe(II) that persists primarily in the phyllosilicate fraction. Color variations reflect grain-size differences that allowed the reduction of fluids from regional fault and basement/fill contacts to permeate coarser-grained Cutler sediments. Hematite and chlorite occur in both red and green sediments but are absent in the bleached sediments. Pervasive hematite in both red and green layers suggests that sediments were hematite-rich before later alteration. Chlorite and smectite are elevated in green samples and inversely correlated with biotite content. Green coloration is generally associated with 1) coarser grain sizes, 2) spatial association with basement contacts, 3) elevated smectite and/or chlorite, 4) less total Fe but greater Fe(II)/Fe(III) primarily in the phyllosilicate fraction, and 5) uranium enrichment. The bleached coloration reflects the removal of pigmentary Fe(III) oxide, while the green coloration is due to the removal of pigmentary hematite and the abundance of Fe(II)-bearing phyllosilicates. Abundant mixed-layer and swelling clays such as smectite, illite/smectite, and chlorite/smectite (including tosudite) dominate the mineralogy of the clay fraction. These results are consistent with other studies demonstrating fault-associated fluid alteration in the Paradox Basin region. However, the pervasive greening was not observed in many of these studies and appears to reflect the unique aspects of the paleovalley system and the importance of biotite alteration to Fe(II)-bearing phyllosilicates.https://www.frontiersin.org/articles/10.3389/feart.2023.1219966/fullred bedsironredoxuraniumclayhydrothermal |
| spellingShingle | Desiree P. Hullaster Gerilyn S. Soreghan Ravi K. Kukkadapu Brock S. Dumont Kato T. Dee Andrew S. Elwood Madden Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration Frontiers in Earth Science red beds iron redox uranium clay hydrothermal |
| title | Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration |
| title_full | Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration |
| title_fullStr | Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration |
| title_full_unstemmed | Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration |
| title_short | Red-green-bleached redox interfaces in the proximal Permian Cutler red beds: implications for regional fluid alteration |
| title_sort | red green bleached redox interfaces in the proximal permian cutler red beds implications for regional fluid alteration |
| topic | red beds iron redox uranium clay hydrothermal |
| url | https://www.frontiersin.org/articles/10.3389/feart.2023.1219966/full |
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