Petrographic evidence for ediacaran microbial mat-targeted behaviors from the great basin, United States

摘要

The lower Member of the Wood Canyon Formation contains a variety of simple late Precambrian-early Cambrian dwelling and grazing traces, typical of early bioturbators. The traces, dominated by Planolites and Palaeophycus, are heavily abundant throughout sections comprised of higher energy siliciclastics. Two of which, Chicago Pass and Boundary Canyon (California, USA), also contain evidence for targeted microbial mat penetration by undermat mining organisms below and into the PC-C boundary. The co-occurence of penetrative burrows within microbial microlaminae, surficial trails, and dwelling structures is characteristic of the complex Ediacaran trace fossil, Lamonte trevallis, as described by Meyer et al., (2014) from the Dengying Formation of South China. The specimens from the Wood Canyon Formation present similar structures resulting from altering behaviors of epibenthic locomotion, undermat mining, and dwelling (Meyer et al., 2014). Principally, grain size analyses confirmed the presence of microbial mat-targeted mining, seemingly resistant to overprinting by co-occurring horizontal traces. Therefore, we have classified the traces present in the California sections as Lamonte trevallis, broadening the geographic extent of this particular mining behavior in the Precambrian and the instances of complex bioturbating behaviors preceding the Cambrian substrate revolution.