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

Abstract

The Steptoean Positive Carbon Isotope Excursion (SPICE) of earliest late Cambrian (Furongian) age is identified in England. The excursion is found within a ca 145 m thick siliciclastic succession within the middle and higher part of the Outwoods Shale Formation of Warwickshire, and reaches a maximum δ 13 C org amplitude of 4.1‰ at values of -25.6‰. Biostratigraphical data show that the excursion occupies the greater part of the Olenus trilobite biozone, an equivalent of the Glyptagnostus reticulatus biozone that marks the base of the Furongian and coeval base of the Steptoean in North America. The amplitude of the excursion approaches that recorded in limestonedominated Laurentian successions, and is greater than that recently documented for organic-rich mudstones of palaeocontinental Baltica in southern Sweden. A minor positive excursion above the SPICE may equate with a similar excursion recognised in Siberia. The SPICE in the Outwoods Shale Formation seems closely linked to the widely recognised early Furongian eustatic sea level rise. There is no evidence in the English succession for slightly later regression, elsewhere considered coincident with the peak of the excursion and pivotal to some previous models explaining the SPICE.Keywords: Cambrian, Furongian, carbon isotope excursion, England, Avalonia Late Cambrian (Furongian) carbonate successions in many parts of the world (North America, Argentina, Siberia, Kazakhstan, China, Australia) contain an interval of markedly positive δ 13 C carb values, peaking at +5‰ (Saltzman et al., 2000;Kouchinsky et al., 2008). More recently, the same positive Carbon Isotope Excursion (CIE) has been identified in organic-rich mudstones of the Alum Shale Formation in southern Sweden, where δ 13 C org peak values are around -28‰ (with a maximum amplitude of around 2‰) (Ahlberg et al., 2009). This CIE, first recognised in the late Cambrian of North America by Brasier (1993) and confirmed as a global CIE by Saltzman et al. (1995), is termed the Steptoean Positive Carbon Isotope Excursion (SPICE) (Saltzman et al., 1998). We report here the occurrence of the SPICE in the Cambrian of central England, the first record in an Avalonian succession. The palaeogeographic setting of these mid-shelf clastic deposits contrasts with 1 areas where the SPICE has previously been identified (e.g. shallow carbonate shelf in North America; shallow, dysoxic-anoxic shelf in southern Sweden). This contrasting setting provides an opportunity to critically assess the likely driving mechanism(s) that created this global isotopic excursion.The SPICE is believed to have had a duration of about 4 Ma (Saltzman et al., 1998), although 3 Ma is probably a better estimate based on dates recently published by Peng and Babcock (2008). In common with other positive CIEs in the geological record, one interpretation of the SPICE is attributed to increased burial of organic carbon, that is enriched in isotopically light 12 C thus increasing the 13 C pool in the oceans. However, terrestrial weathering impacts relate...

Carbon isotopes, stratigraphy, and environmental change: the Middle–Upper Cambrian Positive Excursion (SPICE) in Port au Port Group, western Newfoundland, Canada

“…Additionally, the δ 13 C carb of the SPICE has a relatively lower magnitude than observed in other suggested localities around the world. Globally, the SPICE is described as a δ 13 C carb positive shift of around +5‰ (Saltzman et al 2000, 2004, Kouchinsky et al 2008, Woods et al 2011 in carbonates. The results presented here reach a δ 13 C carb peak of about +1.13 ‰ for the March Point section and +2.2 ‰ (Saltzman et al 2004), and +1.8 ‰ (this work) for the Felix Cove section, with an average shift of about +2 ‰, half of the typical global value.…”

“…Upper Cambrian (Steptoean Stage) carbonate successions are found worldwide, including examples in North America, Siberia, Kazakhstan, China Australia and Oman (Figure 1), with a positive carbonate carbon isotope (δ 13 C carb ) excursion (CIE) of up to +5‰, lasting nearly 4 Ma (Saltzman et al 2000, 2004, Kouchinsky et al 2008, Woods et al 2011, Neilson et al 2016. This excursion has also been observed in the δ 13 C of organic-rich (δ 13 C org ) mudstones and shales (Ahlberg et al 2009, Saltzman et al 2011.…”

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

“…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.…”

“…The later Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE) event is recognized as a global oceanographic event that records large perturbations to the global carbon and sulfur cycles (Gill et al., ; Saltzman et al., ). The SPICE is recorded in globally distributed successions (Figure ), as a large positive shift, of up to +5‰ in the carbon isotopic compositions of marine carbonates (Glumac & Walker, ; Kouchinsky et al., ; Perfetta, Shelton, & Stitt, ; Saltzman, Runnegar, & Lohmann, ; Saltzman et al., ; Schmid, Smith, & Woltering, ; Zhu, Zhang, Li, & Yang, ), organic carbon (Ahlberg et al., ; Hammer & Svensen, ; Li et al., ; Saltzman et al., ; Woods, Wilby, Leng, Rushton, & Williams, ), and inorganic carbon in phosphatic brachiopod shells (Cowan, Fox, Runkel, & Saltzman, ). This excursion spans the Paibian Stage of the Furongian International Series (Peng et al., ).…”

Black shales and other sediments with high organic matter contents in Phanerozoic climatic cycles: Communication 1. Black shales at the Gondwanan stage of biosphere evolution

“…At the same time, no related extinction of marine organisms is observable since the trilobite fauna in the Outwoods Clay is largely represented by olenomorphic taxa (in total 36 species), which preferred relatively deepwater habitat condition. Clays located several meters above the SPICE positive excursion enclose phosphorite concretions and lenses of glauconite sandstone, which may reflect significant decrease in sedimentation rates (Woods et al, 2011). The paragenesis of black shales, phosphorites, and glauconite sands is usually charac teristic of the shelf break zone influenced by upwelling E q u a t o r Siberia Baltica Iapetus Laurentia P a n t h a l a s s a and cold currents being commonly confined to cool ing and sea level fall epochs.…”