The Ediacaran Period

The tempo of Ediacaran evolution

“…We emphasize that the two late Ediacaran negative CIEs (discussed below) proposed in this paper are not compromised by this stratigraphic uncertainty (see the Supplementary Materials). The date of 550.1 ± 0.6 Ma has been interpreted as the terminal timing either of the Shuram (8,11) or of a younger, post-Shuram CIE (1,12,13). These contrasting correlation models highlight the issues of regional complexity in developing regional chronostratigraphic frameworks; however (discussed below), the latter interpretation is preferred in this study.…”

“…The Ediacaran Period [635 to 539 million years (Ma) ago] is a pivotal period in Earth history, archiving the rise of complex macroscopic life (1). This evolutionary milestone occurred in the aftermath of extreme climate perturbations, the Cryogenian snowball Earth events (2), and amid several perturbations to the carbon cycle.…”

“…These are recorded by large carbon-isotope excursions (CIEs) in marine carbonate records, defined as negative and positive deviations in the stratigraphic trend of carbonate-carbon isotope ( 13 C carb ) profiles. These perturbations have been documented worldwide and are commonly used to establish regional to global stratigraphic correlations (1,3,4).…”

“…Integration of Ediacaran datasets from geographically disparate localities has relied upon bio-, litho-, and chemostratigraphic correlation combined with sparse radio-isotopic ages. Within this framework, the Ediacaran has been divided into a lower series characterized by abundant and taxonomically diverse acanthomorphic acritarch assemblages and an upper series with Ediacara-type macrofossils (1). The ca.…”

“…The Shuram CIE, the largest magnitude negative excursion in Earth history with  13 C carb values as low as −12‰ and sustained over considerable stratigraphic thickness, has been a major focus for Ediacaran chronostratigraphic correlation (3,8,9). Occurrence of such a distinct CIE in most of the regions within upper Ediacaran stratigraphy has been used to drive and support global correlation of these sections (1,10). Previous age models, assuming a single CIE, have estimated its onset to between 580 and 560 Ma ago with termination by ca.…”