5 The southern margin of the North American cordillera through time
This session deals with the geologic evolution of the southeastern Cordillera of the North American Plate, its role during ancient orogenic cycles, opening of the Gulf of Mexico, and its interaction with the Caribbean Plate.
Wednesday, 22 April 2026
8:00 AM - 12:00 PM
LMH, Meeting Room
Ediacaran-Cambrian passive margin in Nevada and California
Paper number: 5-8
Program: Technical Sessions
Time: 10:25 AM – 10:45 AM
Authors
Abstract
Cambrian and Ediacaran sequences of California and Nevada lack active volcanics, but have paleovalleys, paleosols, and fluvial facies. Grey stromatolitic dolostone and shale of northern localities (Mt Dunfee and Westgard Pass) were shallow to deep marine, 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 paleoenvironments. 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. These paleosols are aridland Gypsids and Calcids, as well as weakly developed soils, but all with LYREE enrichment and low boron content of soils. Northern Ediacaran marine rocks, in contrast, are limestones with Cloudina and Wyattia, and shales with Conotubus and Wutubus, HYREE enrichment and higher boron. Ediacaran marine wormlike fossils (Wormworld) were ecologically distinct and geographically separated from non-marine, sessile, vendobionts (Mattressland). Lack of volcanism and tectonism in southern California and Nevada during the Ediacaran and Cambrian allowed marine-non-marine interfingering on a tectonically stable passive margin to the North American Plate.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410745
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