High-resolution stratigraphy and correlation of Cambrian strata using carbon isotopes: an example from the southern Appalachians, USA

Abstract

This study presents an example of using well-constrained stratigraphic trends in carbon isotope composition of marine carbonate deposits as a tool for high-resolution correlation of successions that lack prominent biomarkers.

Evidence for the development of local anoxia during the Cambrian SPICE event in eastern North America

“…Previous studies by Glumac and Walker (1998), Glumac (2011), A noteworthy feature of our δ 13 C carb records is the isotopic variability within the overall positive shift associated with the onset of the SPICE in the two cores where measurements were from bulk shale samples (ODGS-3409 and EQT-Big Sandy) as compared to the smoother trend seen in the microdrilled carbonate mudstone record (KGS C-103). As mentioned above, bulk carbonate content of these shales may comprise any combination of detrital carbonate, early marine cements, as well as additional early or late diagenetic carbonate phases.…”

“…Previous studies by Glumac and Walker (), Glumac (), and Gerhardt and Gill () document the onset of the SPICE as a 2‰ shift in δ 13 C carb within the upper 10–20 m of the Nolichucky Formation in outcrop exposures in Tennessee and Virginia. The new subsurface findings presented here from within the Rome Trough and craton‐proximal locations within the Conasauga Basin also document the beginning of the SPICE as a ~2‰ shift in δ 13 C carb (also coupled with an associated rise in δ 34 S py ).…”

“…These biozones represent the last assemblage of the Marjumaniid F I G U R E 1 Paleogeographic reconstruction of the Earth during the late Cambrian (after Blakey and Wong (2003) and Blakey (2008)) depicting locations where the SPICE event has been documented: Northern Laurentia (Saltzman et al, 1998; Southern Laurentia (Cowan et al, 2005;Gerhardt & Gill, 2016;Glumac, 2011;Glumac & Walker, 1998;Hurtgen et al, 2009;Perfetta et al, 1999;Schiffbauer et al, 2017); Baltica (Ahlberg et al, 2009;Gill et al, 2011;Hammer & Svensen, 2017); Australia Lindsay et al, 2005;Saltzman et al, 2000;Schmid et al, 2018); Siberia (Kouchinsky et al, 2008); North China (Bagnoli et al, 2014;Chen, Chough, Lee, & Han, 2012;Ng, Yuan, & Lin, 2014;Zhu et al, 2004); South China (Li et al, 2018;Saltzman et al, 2000); Northwest China (Liu et al, 2017); South Korea (Lim, Chung, Park, & Lee, 2015); Precordillera (Sial et al, 2008); Armorica (Álvaro, Bauluz, Subías, Pierre, & Vizcaïno, 2008); Avalonia (Woods et al, 2011); and Kazakhstan (Saltzman et al, 2000;Wotte & Strauss, 2015). White circles represent studies documenting the SPICE in δ 13 C records, and black stars indicate localities where both carbon and sulfur (δ 34 S) isotopic records have been generated.…”

“…With the exception of outcrop exposures in Appalachian fold‐thrust belt, much of the sedimentary fill of the Conasauga Basin remains in the subsurface. In the outcrops within the fold‐thrust belt, the onset of the SPICE and end‐Marjuman extinction occurs in the upper portion of the Nolichucky Formation (Cuggy, ; Derby, ; Gerhardt & Gill, ; Glumac, ; Glumac & Walker, ). Unfortunately, establishing the biostratigraphic framework in the subsurface relies upon the identification of sparse fossil material from a limited number of borehole locations.…”

The geochemistry of the late Cambrian carbonate in North China: the Steptoean Positive Carbon Isotope Excursion (SPICE) record suppressed in a coastal condition?

“…A series of geochemical perturbations were recorded in the late Cambrian stratum, of which the Steptoean Positive Carbon Isotope Excursion (SPICE) is one of the most intriguing and yet puzzling records because of its dramatic shifts in both carbon and sulphur isotope, worldwide distributions, implications of ocean/atmosphere redox changes, and close connections with the biological extinction/turnover (Saltzman et al 2000(Saltzman et al , 2011Gill et al 2007Gill et al , 2011Hurtgen et al 2009;Maloof et al 2010). The SPICE started at the base of the Paibian Stage, Furongian Series (∼499 Ma), and lasted for 2-4 Ma (Peng et al 2012), which shows a distinct record of 4-6 ‰ positive shift in the carbon isotope of carbonate (δ 13 C carb ) in the strata from Antarctica, Argentina, Australia, England, Poland, France, Spain, Wales, Kazakhstan, Newfoundland, South China, Siberia, Sweden and the USA (Saltzman et al 1998(Saltzman et al , 2004Zhu et al 2004;Cowan et al 2005;Álvaro et al 2007;Glumac & Mutti, 2007;Ahlberg et al 2009;Gill et al 2011;Glumac, 2011;Woods et al 2011;Peng et al 2012;Sial et al 2013;Wotte & Strauss, 2015). A covariation between the SPICE and organic carbon isotopic composition (δ 13 C org ), or the sulphur isotopic composition (carbonate-associated sulphate (δ 34 S CAS ) and sedimentary pyrite (δ 34 S py )) was also reported (Gill et al 2011;Saltzman et al 2011).…”