EDIACARAN LOESS-PALEOSOL SEQUENCES FROM SOUTHERN CALIFORNIA

The basal Ediacaran, dolomitic, Noonday Formation of southern California, has been interpreted as a “cap carbonate” overlying tillite of the Cryogenian Kingston Peak Formation, and as a massive marine whiting precipitated after retreat of Snowball Earth glaciation. However, the grainsize mode in the Noonday Formation is 44-52 μm (coarse silt), and 8-50 % of the grains are quartz and feldspar, most like a loess deposit. Pedogenic carbonate nodules in the Noonday Formation have replacive micritic textures, and strong correlation of stable isotopes of oxygen and carbon in carbonate, unknown in marine carbonate. Paleosols also show light rare earth enrichment, rather than heavy rare earth enrichment of marine rocks. Individual paleosols show surficial clay and iron enrichment, Paleosols of three different kinds are recognized from geochemical, petrographic and granulometric data, and also from permineralized hyphae, spheroidal cells, and thallus organization comparable with lichens. Scanning electron microscope studies also reveal skeletal bipyramidal crystals of whewellite (oxalate) like those of lichen pruina. The fossils are most like modern window lichens (shallow subterranean lichens), and formed nabkhas (vegetation-stabilized dunes) of a loess plateau comparable in thickness and extent to the Chinese Loess Plateau of Gansu.