Environmental and diagenetic variations in carbonate associated sulfate: An investigation of CAS in the Lower Triassic of the western USA

Marenco, Pedro J.; Corsetti, Frank A.; Kaufman, Alan J.; Bottjer, David J.

doi:10.1016/j.gca.2007.10.033

Cited by 78 publications

(43 citation statements)

References 36 publications

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“…Full biotic recovery occurred in the early-middle Triassic where ␦ 34 S values returned to Ϸ18 per mil (46). This pattern has been explained by mixing of isotopically enriched sulfate from an anoxic-sulfidic deep ocean onto the shelf, where it is then captured in evaporites and as a structural component of carbonate minerals (so-called ''CAS''; CAS itself should be a minor sink for sulfate) (45,47). The model here provides an alternative explanation.…”

Section: Model Results and Discussionmentioning

confidence: 80%

“…The recovery was slow, taking some 4 million years (44). Sulfate concentrations are not constrained through this time interval, but the isotope record of seawater sulfate shows a rapid increase from low ␦ 34 S values of Ϸ17 permil at the Permian-Triassic boundary to up to 38 per mil in the Spathian some 3-4 million years later (45). Full biotic recovery occurred in the early-middle Triassic where ␦ 34 S values returned to Ϸ18 per mil (46).…”

Section: Model Results and Discussionmentioning

confidence: 98%

See 1 more Smart Citation

Animal evolution, bioturbation, and the sulfate concentration of the oceans

Canfield

Farquhar

2009

Proc. Natl. Acad. Sci. U.S.A.

444

270

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As recognized already by Charles Darwin, animals are geobiological agents. Darwin observed that worms aerate and mix soils on a massive scale, aiding in the decomposition of soil organic matter. A similar statement can be made about marine benthic animals. This mixing, also known as bioturbation, not only aides in the decomposition of sedimentary organic material, but as contended here, it has also significantly influenced the chemistry of seawater. In particular, it is proposed that sediment mixing by bioturbating organisms resulted in a severalfold increase in seawater sulfate concentration. For this reason, the evolution of bioturbation is linked to the significant deposition of sulfate evaporate minerals, which is largely a phenomena of the Phanerozoic, the last 542 million years and the time over which animals rose to prominence.Phanerozoic ͉ evaporite ͉ gypsum ͉ sulfate reduction W ith a current concentration of 28 mM, sulfate is the second most abundant anion in seawater. Sulfate enters the ocean mostly from river runoff, with minor contributions from volcanism (1). It leaves the ocean as either pyrite (FeS 2 ) buried in sediments, formed as a product of microbial sulfate reduction, or as sulfate minerals, mostly gypsum (CaSO 4 ⅐5H 2 O), in evaporite deposits (2). Gypsum precipitates before halite (NaCl) and becomes an important evaporite component when the ion product (IP CaSO4 ) between Ca 2ϩ and SO 4 2-in unevaporated seawater exceeds 23 mM 2 (3); presently IP CaSO4 is 280 mM 2. The concentration of Ca 2ϩ has varied between 10 and 40 mM over the last 550 million years (4), and if this range applies through Earth history, IP CaSO4 would exceed 23 mM 2 with relatively low SO 4 2-levels of 0.5 to 2 mM. If sulfate concentrations fall below this level or if IP CaSO4 becomes Ͻ23 mM 2 , the chances for gypsum supersaturation during evaporation of seawater is reduced. The total amount of gypsum deposition from any given parcel of seawater is also limited by sulfate concentration.Previous studies have documented little evidence for gypsum deposition before the Mesoproterozoic (1.6 to 1.0 billion years ago) suggesting reduced seawater sulfate concentrations before this time (5). This analysis is predicated on the assumption that observations of gypsum abundance faithfully represent the original magnitude of gypsum deposition. However, it is known that gypsum is easily dissolved during weathering (6), and alternative approaches have been developed to evaluate the history of gypsum deposition. One of these derives the history of gypsum deposition from the isotope record of sulfate and sulfide ( Fig. 1) (1), with the fraction of the total sulfur leaving the oceans as pyrite given by the equation:

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Section: Model Results and Discussionmentioning

confidence: 80%

Section: Model Results and Discussionmentioning

confidence: 98%

Animal evolution, bioturbation, and the sulfate concentration of the oceans

Canfield

Farquhar

2009

Proc. Natl. Acad. Sci. U.S.A.

444

270

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show abstract

“…For instance Kaufman et al (1993) suggest Mn/Sr < 10 and d 18 O more positive than À10& will reflect diagenetic recrystallization likely to preserve primary d 13 C. Mn/Sr < 2-3 are more typical used when looking at Sr-isotope composition because strontium is in low abundances in rock material and thus easily altered (cf., Banner and Hanson, 1990). In addition, and trying to constrain dolomitization, Ca/Mg is considered as well, with a Ca/Mg > 50 as a reflection of only minor dolomitization (Marenco et al, 2008a).…”

Section: Diagenetic Constraintsmentioning

confidence: 99%

Paired δ34S data from carbonate-associated sulfate and chromium-reducible sulfur across the traditional Lower–Middle Cambrian boundary of W-Gondwana

Wotte

Strauß

Fugmann

et al. 2012

Geochimica et Cosmochimica Acta

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“…Carbonate-associated sulfate (CAS) has emerged as popular proxy for the sulfur isotope composition of ancient seawater (Burdett et al, 1989;Kampschulte et al, 2001;Hurtgen et al, 2002Hurtgen et al, , 2004Kah et al, 2004;Kampschulte and Strauss, 2004;Newton et al, 2004;Gellatly and Lyons, 2005;Fike et al, 2006;Riccardi et al, 2006;Gill et al, 2007;Marenco et al, 2008;Fike and Grotzinger, 2008). CAS occurs as a trace constituent within carbonate minerals, substituting for the CO 3 À2 group (Takano, 1985;Pingitore et al, 1995), and modern carbonates typically contain CAS concentrations of 1000-10,000 ppm (Burdett et al, 1989;Staudt and Schoonen, 1995;Kampschulte et al, 2001;Lyons et al, 2004).…”

Section: Introductionmentioning

confidence: 99%