Stable Isotopes of Carbon and Oxygen in Modern Sediments of Carbonate Platforms, Barrier Reefs, Atolls and Ramps: Patterns and Implications

Abstract

Stable isotopes of carbon (δ horizon. Above the meteorically influenced section, however, variability along individual cores is comparably low (<1.2‰). The enormous carbon and oxygen isotopic variability observed in modern shallow water carbonates as compared to fossil sections, where δ 13 C is used as stratigraphic marker, is probably a result of as yet poorly defined taphonomic and diagenetic filters, which significantly reduce isotopic variability.

Eolian dust influx and massive whitings during the kozlowski/Lau Event: carbonate hypersaturation as a possible driver of the mid-Ludfordian Carbon Isotope Excursion

“…In the case of the mid-Ludfordian CIE, the maximum δ 13 C values have been noted (Wigforss-Lange 1999) in the shallowest zone of the semi-enclosed (Baltic) foreland basin, which shows analogy to the most 13 C-enriched Recent marine carbonates (e.g. oolites) observed in the semi-enclosed foreland basin of the Persian Gulf (Gischler et al 2007).…”

“…This should cause high residence time of the water pool, what along with documented here surface-water precipitation events could cause the isotope fractionation of the DIC in the entire basin during the studied event. It is important to note that the foreland basins with widespread carbonate production often contain relatively 13 C-enriched carbonates (recent Persian Gulf - Gischler et al 2007, Miocene Parathetys Sea -Harzhauser Figure 10. A hypothetical palaeoceanographic (early Palaeozoic) model for the concurrent multi-way development of the supersaturation state during the glaci-eustatic sea-level fall (A); followed by (B) the formation of a synchronous, spatially detached CIE due to massive carbonate precipitation on reflooded carbonate platforms.…”

“…Both values are 2-3‰ heavier in relation to the maximum δ 13 C values (~8.5‰) obtained from brachiopod shells from the mid-Ludfordian CIE interval of Gotland (Samtleben et al 2000), which probably are close to the isotope composition of the DIC. The difference is probably caused by the typically heavier isotope signatures of microbially induced precipitates in relation to the δ 13 C of the DIC (Thompson et al 1997, Gischler et al 2007.…”

Whiting-related sediment export along the Middle Miocene carbonate ramp of Great Bahama Bank

“…the Bahamas (Weber 1967;Swart and Eberli 2005;Swart et al 2009), Australia (Weber and Woodhead 1969;Dix et al 2005), and selected places at Belize, Maldives, and Kuwait (Gischler et al 2009). The origin of the 13 Cenriched values of aragonite on GBB is not well understood.…”

Facies development and sequence stratigraphy of the Ludfordian (Upper Silurian) deposits in the Zbruch River Valley, Podolia, western Ukraine: local facies overprint on the δ13Ccarb record of a global stable carbon isotope excursion

“…Very good geochemical, biostratigraphical, and paleoecological documentation exists for the Lau excursion, and it is often used as a model to study positive CIEs, which are widely used as chemostratigraphic markers and as indicators of perturbations of the global carbon cycle (Jeppsson 1990;Aldridge et al 1993;Bickert et al 1997;Jeppsson and Aldridge 2000;Munnecke et al 2003;Calner 2005a;Melchin and Holmden 2006;Cramer and Saltzman 2007a, b;Fanton and Holmden 2007;Calner et al 2008;Małkowski et al 2009;Kozłowski and Sobień 2012). Studies of recent and sub-fossil carbonate sediments indicate that sea-level forcing, restricted circulation and laterally variable sediment composition can significantly influence the d 13 C carb values, leading to amplification of positive excursions in carbonate platform interiors during flooding intervals (Immenhauser et al 2003;Swart and Eberli 2005;Swart 2008;Gischler et al 2009;Oehlert et al 2012). The small-scale spatial variability of d 13 C values results from a combination of generic marine-water signal and local factors such as facies, restricted circulation, and diagenetic overprint.…”