Chapter 8Productivity and bottom water redox conditions at the Frasnian-Famennian boundary on both sides of the Eovariscan Belt: constraints from trace-element geochemistry

Diagenetic versus detrital origin of the magnetic susceptibility variations in some carbonate Frasnian–Famennian boundary sections from Northern Africa and Western Europe: implications for paleoenvironmental reconstructions

“…An associated enhancement of the carbonate productivity is emphasized by the maximum contribution of the diamagnetic component to the MS. Significant positive anomalies in the barium concentration (Tribovillard et al 2004;Riquier et al 2005), as well as the widespread occurrence of algal blooms in the KW-type horizons (Paris et al 1996;Gong et al 2002) corroborate this high primary productivity in the Late Frasnian oceans.…”

“…These horizons have been described in many sections, located in outer shelf (i.e., 100-200 m depth) and epicontinental basin settings, mainly along the former Prototethysian margins of Laurussia (Northern America, Northern Europe) and Gondwana (Southern Europe, Northern Africa). For all these sites, geochemical proxies for depositional redox conditions and primary productivity show consistent anomalies indicating general oxygen-depleted bottomwater along continental margins and increased marine productivity (Murphy et al 2000;Tribovillard et al 2004;Riquier et al 2005). On top of the KW levels, however, the basal Famennian times are marked by a pronounced depositional break, with frequent hiatuses and breccia developed during a significant worldwide sea-level fall (Isaacson et al 1999;Casier et al 2000;Devleeschouwer et al 2002;Sandberg et al 2002).…”

“…Within the data set, very few samples display higher coercivities. Most of these few samples were collected within the KW horizons, which have been shown to develop under dysoxic to anoxic conditions (e.g., Riquier et al 2005). As illustrated by rock magnetic analyses in recent sapropel-type levels (Roberts et al 1999;Passier et al 2001), such highly reducing depositional conditions suggest that the high-coercivity phase in these levels could be partly composed of ferromagnetic iron sulphides (Fe monosulfides), ultimately transformed into diagenetic pyrrhotite (Fe 7 S 8 to Fe 11 S 12 ).…”

Trace element and REE geochemistry of the Ediacaran Doushantuo Formation from Fanjingshan area, northeast Guizhou province, China

“…For most of sedimentary deposition, aluminum can be considered as an indicator of the aluminosilicate fraction of the sediments, with very little ability to move during the diagenesis (Brumsack 1989;Calvert and Pedersen 1993;Morford and Emerson 1999;Piper and Perkins 2004). Though the method is commonly used for analyzing the paleoenvironmental condition of fine-grained siliciclastic sediments and sedimentary rocks relatively rich in OM, such as gray and black shales (e.g., Rimmer 2004;Rimmer et al 2004;Algeo and Maynard 2004;Tribovillard et al 2004a, b;Riquier et al 2005), recent studies have applied this method to carbonate rocks, especially Neoproterozoic cap carbonate (e.g., Font et al 2006;Nédélec et al 2007;Huang et al 2009Huang et al , 2012Meyer et al 2012).…”

Geochemical characteristics of Late Permian sediments in the Dalong Formation of the Shangsi Section, Northwest Sichuan Basin in South China: Implications for organic carbon-rich siliceous rocks formation

“…Thus major and trace-element geochemistry can be taken as proxies for reconstruction of paleo-depositional conditions, such as paleoproductivity, paleoredox condition and influence of hydrothermal (hot water) activities (e.g., Algeo and Maynard, 2004;Bostrom et al, 1973Bostrom et al, , 1979Crerar et al, 1982;Nameroff et al, 2004;Pen et al, 1999;Tribovillard et al, 2006). Nutrient-type elements such as Ni, Cu, Zn, Ba, Cd, P, and Fe might enrich due to organic matter enrichment (McManus, et al, 1999;Piper and Perkins, 2004;Riquier et al, 2005; Sections and Points (GSSPs) for the P/T boundary strata in China (Yin et al, 2001). Detailed lithological and biostratigraphic investigation works have been done which include paleomagnetic study and the conodont evolution from the P/T transitional section (Li et al, 1988;Yao et al, 1992), changes in carbon and oxygen isotopes, and the iridium anomaly in the P/T boundary clay rocks (Gao et al, 1987;Huang, 1992;Li et al, 1986).…”