Ediacaran-Cambrian paleosols of Nevada and California

Abstract

The Cambrian and Ediacaran sequence of California and Nevada is rife with unconformities, paleovalleys, paleosols, and fluvial facies. This study confirms shallow marine environments for grey stromatolitic dolostone and shale of northern localities (Mt Dunfee and Westgard Pass), but fluvial red sandstones and siltstone of southern localities (Johnnie, Eagle Peak, Emigrant Pass, Donna Loy, and Cadiz) include paleosols as evidence for coastal plain and fluvial environments. Three marine transgressions into the southern localities, were in Ediacaran Johnnie Formation, earliest Cambrian Manykodes pedum zone, and Early Cambrian Olenellus trilobite zone. The southern locations have paleosols with Ediacaran fossils Ernietta, Pteridinium, Swartpuntia, and Hallidaya in growth position, as evidence that these vendobiont fossils were non marine. The paleosols include aridland Gypsids and Calcids, as well as weakly developed soils, with diagnostic LYREE enrichment, and low boron content of paleosols. Northern Ediacaran marine rocks, in contrast, are limestones with Cloudina and Wyattia, and shales with Conotubus and Wutubus. Identical marine and non-marine facies and biotas are also known from Ediacaran and Cambrian rocks of Namibia. Ediacaran marine wormlike fossils (Wormworld) were ecologically distinct and geographically separated from non-marine, sessile, vendobionts (Mattressland).

Fig 1. Examined localities in southern California and Nevada, USA.

Fig 2. Field photographs of

(A) Cambrian sequence around red bed paleosols of the Carrara Formation in Emigrant Pass; (B) late Ediacaran sequence near Donna Loy Mine, California; (C) Cambrian sequence near Cadiz, California; (D) Hebinga loam paleosol in Stirling Quartzite near Donna Loy Mine (45 m in Fig 3A); (E) Duhubite loam paleosol with surface desert pavement in Lower Member of Wood Canyon Formation west of Johnnie, Nevada; (F) Buinga sandy loam in Zabriskie Quartzite near Cadiz (19 m in Fig 3C); (G) red bed paleosols (Bui silty clay loam, Angebite silty clay loam, Pohonta silty clay loam, on Wookki silty clay loam) in Carrara Formation in Emigrant Pass (74 m in Fig 3B). Notations in white (D-G) are soil horizon interpretations based on petrographic and geochemical data (Figs 6-7).

Fig 3. Measured sections at Donna Loy Mine (A), Emigrant Pass (B), and Cadiz (C) showing lithologies and stratigraphic levels of paleosols. Development and calcareousness by reaction with dilute HCl are from scale of Retallack (2012). Munsell Hue is from Munsell Color Company.

Fig 4. Polished slabs of paleosols and sedimentary beds: A, Hebinga loam paleosol in Stirling Quartzite Donna Loy Mine (45 m in Fig 3A), showing radial gypsum pseudomorphs; B, Duhubite loam paleosol with vesicular structure at arrows, in Wood Canyon Formation, Donna Loy Mine (79 m in Fig 3A); C, Buinga sandy loam paleosol, Zabriskie Quartzite, Cadiz (19 m in Fig 3C); D, radial gypsum pseudomorph in Hebinga paleosol 2 miles southwest of Johnnie; E, Nataanga loam paleosol in Wood Canyon Formation, Donna Loy Mine (99 m in Fig 3A), in vertical (D) and horizontal section

(E).

Fig 5. Oriented thin sections cut vertical to bedding: A, intertextic mosepic plasmic fabric in Bw horizon of Hebinga loam paleosol, Stirling Quartzite, near Donna Loy Mine (45 m in Fig 3A); B, surface cracking and oxidation, A horizon of Bui silty clay loam, Carrara Formation, in Emigrant Pass (72 m in Fig 3B); C, ferruginized dolostone clasts faceted on top, A horizon of Duhubite loam paleosol, Upper Member of Wood Canyon Formation, near Donna Loy Mine (79 m in Fig 3A); D, shell fragments in A horizon of Pakuitah silt loam paleosol, Chambless Limestone near Cadiz (42 m in Fig 3C); E, graded bedding within varves and soft sediment deformation preserved in C horizon of Wookki silty clay loam paleosol, Carrara Formation, in Emigrant Pass (71 m in Fig 3B); F, syntaxial quartz overgrowth cement on dusty rim of original grain, A horizon of Naatanga loam paleosol, Wood Canyon Formation, near Donna Loy Mine (99 m in Fig 3A);G, silt sized, subrounded rhombs of dolomite, A horizon of Duhubite loam paleosol.

Wood Canyon Formation, near Donna Loy Mine (79 m in Fig 3A). Specimens in the Museum of Natural and Cultural History, University of Oregon, Eugene are A, R5354; B, R5832; C, R5852; D, R5816; E, R5844; F, R5356; G, R5852.

Fig 6. Ediacaran paleosol profiles their petrographic composition from point counting thin sections, and weathering trends revealed by molecular weathering ratios (

Tables S1-S2). Stratigraphic levels of these profiles are labelled in Fig 3. For field photos of two of the paleosols see Fig 2D-E, and for photomicrographs see Fig 5A, C, F-G.

Fig 7. Cambrian paleosol profiles their petrographic composition from point counting thin sections, and weathering trends revealed by molecular weathering ratios (

Tables S1-S2). Stratigraphic levels of these profiles are labelled in Fig 3. For field photos of two of the paleosols see Fig 2F-G, and for photomicrographs see Fig 5B, D-E.

Fig 8. Tau analysis of Ediacaran and Cambrian paleosols of California, including elemental mass transfer versus strain

(A), and versus depth in paleosol profiles (B).

Fig 9. Covariance of carbon and oxygen isotopic composition of carbonate as a characteristic of paleosols, rather than other settings: A, paleosols of the Cambrian Carrara Formation [152], of the Ediacara Member of South Australia [140], of the Cambrian Arumbera Formation at Ross River [89], of the Ordovician Juniata Formation of Pennsylvania [26], and of the Silurian Bloomsburg Formation of Pennsylvania [25]; (B), soil nodules (above Woodhouse lava flow, near Flagstaff, Arizona [156] and in Yuanmou Basin, Yunnan, China [155]; (C), soil crusts on basalt (Sentinel Volcanic Field, Arizona, from [156]); (D), Quaternary marine limestone altered diagenetically by meteoric water (Key Largo, Florida, [139], and Clino Island, Bahamas, [158]); (E), Holocene (open circles) and Ordovician (open squares) unweathered marine limestones [154] and Early Cambrian (closed circles), Ajax Limestone, South Australia [153]; (F), marine methane cold seep carbonate, Miocene, Santa Cruz Formation, Santa Cruz, California [161] and Pliocene, Quinault Formation, Cape Elizabeth, Washington [162].

Slope of linear regression (m) and coefficients of determination (r²) show that carbon and oxygen isotopic composition is significantly correlated in soils and paleosols, but not in other settings.

Fig 10. Rare earth element analyses of Ediacaran paleosols compared with Cambrian marine sandstone: A, Hebinga loam paleosol in Stirling Quartzite near Donna Loy Mine, and B, Aisen and Naatanga silt loam paleosols in the Lower Wood Canyon Formation near Donna Loy Mine, and multiple levels of sandstone bed with Bergaueria and Wyattia in Upper Member of the Wood Canyon Formation in Emigrant Canyon.

This Aisen profile includes Ernietta in place (specimen F123791A). Numbers after the labels are LYREE/HYREE ratios, which are 3 or more for soils and paleosols, but less than 3 for marine rocks.

Fig 11. Ediacaran and Cambrian fossils and sedimentary structures of southern California: A, Hallidaya brueri discoids from Stirling Quartzite near Donna Loy Mine (45 m in Fig 3A); B, Swartpuntia germsi from Poleta Formation near Westgard Pass; C, Bergaueria hemispherica burrow and Wyattia reedensis conical hyoliths, from the Cambrian Upper Member of the Wood Canyon Formation in Emigrant Pass (21 m in Fig 3B); D, Ernietta plateauensis (sack shaped) and Pteridinium simplex (elongate and strongly fluted) showing pleating and basal seam at angle to bedding, from Lower Member of Wood Canyon Formation south of Johnnie; E-G, Ernietta plateauensis bulbs in life position (E), bulb and leaf bases on bedding plane (F) and leaves protruding for bed top among ventifacted pebbles (G) from Lower Member of Wood Canyon Formation west of Johnnie, Nevada; H, mudcurls within mudcracks (invalid trace fossil name “Manchuriophycus”) from west of Johnnie; I, Rivularites repertus microbial earth structure from west of Johnnie.

Formations of these specimens are Ediacaran Stirling Quartzite (A), Cambrian Poleta Formation (B), Cambrian Upper Member of Wood Canyon Formation (C), and Ediacaran Lower Member of Wood Canyon Formation (E-I). Specimen numbers are A, F123781 Museum of Natural and Cultural History, University of Oregon, Eugene; B, F37450 Museum of Paleontology, University of California Berkeley image courtesy of Dave Strauss; D, USNM 642300 Paleobiology Smithsonian Institution Museum of Natural History; C, E-G, Museum of Natural and Cultural History, University of Oregon, Eugene, F126060 (C), F130202 (E), F130207 (F), F130201 (G). H and I are field photos.

Fig 12. Paleogeographic map for 520 Ma (A) by Ron Blakey, and reconstructions of soils for Late Ediacaran (B, 550 Ma) deposition of Lower Wood Canyon Formation, and Cambrian deposition of Carrara Formation and Latham Shale (C, 515 Ma).

Map reproduced from Colorado Geosystems Inc. under license #20110385-P. The map is in modern geographic coordinates with state outlines, but during the Ediacaran and Cambrian the coast was not north-south, but east-west near the equator (Torsvik and Cocks 2013; Scotese 2021).