The Late Cambrian Spice ( 13C) Event and the Sauk II-SAUK III Regression: New Evidence from Laurentian Basins in Utah, Iowa, and Newfoundland

Abstract

Carbon isotope data from Upper Cambrian sections in three Laurentian basins in northern Utah, central Iowa, and western Newfoundland record a large positive ␦ 13 C excursion (SPICE event) of up to ؉ 5‰. Peak ␦ 13 C ratios are well dated by trilobite collections to the middle of the Steptoean Stage (Dunderbergia Zone) and occur during maximum regression associated with formation of the Sauk II-Sauk III subsequence boundary on the North American craton. Maximum regression was marked by an influx of quartz sand into carbonate-platform settings in all three widely separated basins. In northern Utah, this quartz sand formed a thick sequence known as the Worm Creek Quartzite, which marks a conspicuous interruption of carbonate deposition during the Middle to Late Cambrian in the region. In western Newfoundland, the thickness of the quartz sand unit is much reduced but still marks a brief shutdown of the carbonate factory that is unique to the Cambrian shelf succession of the area. In the central Iowa area of the cratonic interior, an upward-shallowing carbonate succession culminates in cross-stratified trilobite grainstones at the peak of the SPICE in Dunderbergia Zone time, and the lowest point on the relative-sea-level curve is associated with the occurrence of coarse quartz sand derived from the encroaching shoreface.Although it is difficult to determine precisely the departure from baseline ␦ 13 C that marks the beginning of the SPICE excursion in the stratigraphic successions analyzed, our results are consistent with a rise and subsequent fall in ␦ 13 C tracking a major regressive-transgressive event recorded across northern Laurentia. The correlation of a major ␦ 13 C excursion with regression is similar to that described for the Late Ordovician, for which the pattern has been attributed to either increased carbonate relative to terrigenous weathering rates as ice sheets covered up organic-matter-containing silicates at high latitudes or high productivity and organic-carbon burial driven by oceanic overturn. The lack of known Steptoean-age ice sheets that could have affected the ratio of carbonate to silicate weathering rates suggests that organiccarbon burial was the likely cause of the SPICE event. We suggest that increased weathering and erosion rates during relative sea-level fall (Sauk II-III) increased the burial fraction of organic carbon in an expanded region of fine-grained siliciclastic deposits in shelf and upper slope environments during the Steptoean.

The SPICE carbon isotope excursion in Siberia: a combined study of the upper Middle Cambrian–lowermost Ordovician Kulyumbe River section, northwestern Siberian Platform

“…It is represented by minimum values of −3 ‰ to −4 ‰ in Australia Miller et al 2006; Fig. 4) or a less pronounced trough in Laurentia (Buggisch, Keller & Lehnert, 2003;Saltzman et al 2004;Miller et al 2006; Fig. 4).…”

“…The Steptoean positive carbon isotopic excursion (SPICE) is an excellent global chemostratigraphic marker in the upper Cambrian, usually rising far above the background noise (e.g. Saltzman et al 2000Saltzman et al , 2004. Documentation of the SPICE excursion from Siberia is valuable for correlation of richly fossiliferous Siberian sections with other well-known Cambrian sections globally, and therefore contributes much to understanding of biotic evolution, oceanography, climate, tectonics and magnetic field at this time in Earth history.…”

The Furongian (late Cambrian) Steptoean Positive Carbon Isotope Excursion (SPICE) in Avalonia

“…This nutrient pulse could have resulted in a surge of biological productivity, creating the SPICE. Saltzman et al (2000Saltzman et al ( , 2004 discussed the potential role of globally enhanced weathering of isotopically heavy marine carbonates linked to a glacial event as a driver for the SPICE. Although supporting evidence for this appears to be provided by a purported widespread sea level fall (of about 25 m; Saltzman et al, 2000) that coincides with the peak of the SPICE, there is no unambiguous evidence for a high latitude ice sheet in the late Cambrian (Saltzman et al, 2000).…”

“…Although there appears to be a general consensus that the peak of the SPICE coincided with a global sea level lowstand, this scenario requires differing palaeoenvironmental interpretations for lithologically similar units; shale/wackestone-dominated sediments deposited at the onset of the SPICE in North America reflect drowning of the carbonate shelf, whilst similar lithofacies at the peak of the SPICE are believed to represent lowstand deposits, the latter based largely on the presence of an inferred coeval hiatus in trilobite faunas and missing δ 13 C SPICE in North American cratonic successions (Saltzman et al, 1998). Other evidence cited in favour of global late Cambrian regression includes carbonate platform exposure in Queensland and seamount-margin collapse in Kazakhstan (Cook et al, 1991;Saltzman et al, 2004).Whatever theory is advanced to explain the SPICE, it needs to take account of strong circumstantial evidence for a link with changes of diversity in trilobite populations (Saltzman et al, 1998; Zhu et al, 2006). After an initial extinction event, at the onset of the SPICE, some studies have recorded a diversification of trilobite faunas through the overlying succession occupied by the excursion, with peak diversity coinciding with the peak of the excursion (Saltzman et al, 2000).…”

Stable Carbon Isotope Stratigraphy of the Cambrian Machari Formation in the Yeongweol Area, Gangweon Province, Korea

“…C values or lead to higher sedimentation rates that can enhance burial rate of organic matter (Kump and Arthur, 1999;Saltzman et al, 2004). Higher input of land-derived sediments during regression may result in increase of (1) nutrient supply to the ocean, (2) primary production, and (3) carbon burial.…”