CHRONOSTRATIGRAPHY OF THE LATE EDIACARAN - EARLY CAMBRIAN CHILHOWEE CLASTIC SUCCESSION OF SOUTHERN LAURENTIA: REDUX WITH REFINEMENT
Extrapolating from constrained dates and relative positions, key lithostratigraphic events (base of facies/unit) from old to young are: Unicoi/Cochran/Weverton Fm. ca. 553±5 Ma; amygdaloidal basalts of the middle-Unicoi, ca. 547 Ma; first fully marine deposits, upper-Unicoi, ca. 540 Ma. Hampton/Nichols/Harpers Fm., middle Fortunian, ca. 533 Ma. Cambrian Agronomic Revolution, middle Hampton/Nichols/Harpers Fm., middle Cambrian Stage 2, ca. 526 Ma. Nebo/Erwin/Antietam Fm. near base of Cambrian Stage 3, ca. 521 Ma; Murray/lower-mid Erwin/lower mid-Antietam Fm., lower-mid of Cambrian Stage 3, ca. 518 Ma; Hess/mid-upper Erwin/mid-upper Antietam Fm., upper-middle Cambrian Stage 3, ca. 517 Ma; Helenmode/upper Erwin/upper Antietam Fm., lower-mid of Cambrian Stage 3, ca. 516 Ma; Shady/Tomstown Dolomite. upper Cambrian Stage 3, ca. 514 Ma.
This chronostratigraphic framework allows for higher-resolution, global correlation of macroevolutionary and geologic events observed in southern Laurentia during the late Ediacaran to early Cambrian transition.