Small shelly fossils from the Montezuman–Delamaran of the Great Basin in Nevada and California

Abstract

AbstractThe mixed carbonate-siliciclastic successions of the Cambrian Series 2–Cambrian Series 3 interval of the Great Basin are well investigated in respect to their trilobite and brachiopod fauna. In contrast, the small shelly fossils have been mostly unreported. Nine sections in eastern California and southern Nevada have produced a small shelly assemblage of low diversity, which likely reflects non-phosphatization and loss of originally calcareous remains. From the Montezuman–Delamaran stages we reportAnabarella chelataSkovsted, 2006a,Costipelagiella nevadenseSkovsted, 2006a,Pelagiellaaff.P. subangulata(Tate, 1892),Microcornussp.,Parkulasp.,Hyolithellus? sp.,Alloniasp.,Chancelloriasp.,Archiasterellacf.A. hirundoBengtson in Bengtson et al., 1990,Archaeooidescf.A. granulatusQian, 1977, and undefined echinoderms and helcionelloid molluscs. The lower part of the Montezuman Stage delivered a number of lobopodian sclerites asMicrodictyon rhomboidaleBengtson, Matthews, and Missarzhevsky, 1986,Microdictyon montezumaensisn. sp., andMicrodictyon cuneumn. sp. The occurrence ofP. aff.P. subangulataand species ofMicrodictyonin the lower Montezuman Stage offers a fundamental potential for correlation with the base of Cambrian Series 2/Stage 3 of South China, Siberia, and Avalonia.