Application of redox sensitive proxies and carbonate clumped isotopes to Mesozoic and Palaeozoic radiaxial fibrous calcite cements

Abstract

22Ancient marine radiaxial calcite cements are commonly exploited as archives of marine porewater properties 23 based on the argument that they lack metabolic effects often assigned to biogenic carbonates. Here we 24 critically test the significance of conventional versus (with respect to these fabrics) less-conventional proxy 25 data from Pennsylvanian, Triassic, and Cretaceous case examples. Conventional proxies include: 26 cathodoluminescence, carbon and oxygen isotope ratios, main and trace elemental concentrations. Less 27 conventionally applied proxies are: clumped isotope "47", redox-sensitive, and rare earth elements sampled 28 across a succession of Triassic radiaxial fibrous calcites. Radiaxial calcites are subdivided in three groups 29 based on their luminescence characteristics: non-luminescent, patchy luminescent, and bright luminescent.

Evidence for a composite organic–inorganic fabric of belemnite rostra: Implications for palaeoceanography and palaeoecology

“…3D-E, 5A, D, 6) suggest that both phases precipitated from one fluid, or different fluids with near-identical geochemistry. This is, of course, within the limitations of the geochemical resolution of the cathodoluminescence method and with reference to elements that affect luminescence patterns (e.g., Mn 2+ , Fe 2+ and REE; see discussion in Barbin 1991Barbin , 1993Ritter et al, 2015). Conversely, the organic matter-rich triangles display a moderately brighter blue luminescence pattern (Fig.…”

What do we really know about early diagenesis of non-marine carbonates?

“…Furthermore, even when no visible arguments are found for diagenetic alteration Ritter et al, 2015), for example, when replacement calcite inherits both textural and chemical properties of the precursor; very localized, open-system behavior may still cause resetting of an initial geochemical signal (Bajo et al, 2016). It is then only by a careful comparison of different geochemical proxies along the same transect that localized domains of post-depositional alteration can be identified (Bajo et al, 2016).…”

“…In addition, an experimental approach, using in-vitro (Pedley, 2014;Mercedes-Martín et al, 2016) and in-situ (Melim and Spilde, 2011;Boch et al, 2015) setups could help detangle the exact diagenetic pathways (Ritter et al, 2017), controlling parameters and rates of individual processes, across the continuum of non-marine carbonate depositional contexts. A better understanding of the short-lived, intermediate steps and diagenetic products, and the effects on individual geochemical proxies Ritter et al, 2015) is needed to bridge a growing gap between field and lab-based studies at the nanoscale, mostly focussed on the very first steps of carbonate nucleation and precipitation (Benzerara et al, 2006;Sánchez-Román et al, 2011;Krause et al, 2012;Roberts et al, 2013;Burne et al, 2014;Brauchli et al, 2016;Pace et al, 2016), and the rock record of possibly diagenetically modified carbonate deposits, used -or not -in paleoclimatic and -environmental studies.…”

Kapcsolt izotópok (clumped isotopes) a földtudományi kutatásokban

“…Meghatározható a diagenetikus folyamatok során kivált cementek kristályosodási hőmérséklete, az átkristályosodás hőmérséklete, illetve ezekből az eredeti fluidum oxigén-izotópos összetételét is vissza lehet szá -molni (DALE et al 2014, RITTER et al 2015. Karbonátos konkréciók vizsgálatával DALE et al (2014), illetve HEIMHOFER et al (2017 kréta időszaki palák diagenezistörténetét tudta rekonstruálni.…”