THE RELIABILITY OF THE SPICE AS A GLOBAL CORRELATION TOOL: CASE STUDY FROM NORTHERN UTAH
The SPICE in N. Utah occurs over the fossiliferous, carbonate-siliciclastic upper Nounan Fm and overlying Worm Creek Mbr of the St. Charles Fm, spanning the Crepicephalus–Elvinia biozones. This heterolithic succession allows for a robust chronostratigraphic constraint of the SPICE through trilobite biostratigraphy, chemostratigraphy, and high-precision CA-IDTIMS DZ (detrital zircon) MDAs (maximum depositional ages).
We build upon prior work by integrating δ13C and biostratigraphy with CA ID-TIMS DZ MDAs coincident with the onset and falling limb of the SPICE. This provides the only numerical age for the onset of the SPICE. These data further invalidate the correlation of the SPICE and the base of the Pterocephaliid biomere. These new MDAs also provide numerical constraints on the Laurentian biozone schema as well as requiring the revision of the late Cambrian Geologic Time Scale boundaries by 105-106 years.
While we are not arguing an inherent issue with the SPICE itself, rather its correlation, we charge stratigraphers using chemostratigraphic features as correlation tools to recognize the caveats associated with these correlations especially in context of recent paradigm shifting perspectives.