Strontium isotope profile of Carboniferous-Permian Akiyoshi Limestone in southwest Japan.

Abstract

The chemical and Sr isotope compositions of the Akiyoshi Limestone (SW Japan) were deter mined. This limestone is a continuous sequence ranging in age from Early Carboniferous to Late Per mian and is considered as an organic reef complex deposited on a basaltic seamount.

Permian strontium isotope stratigraphy

“…These overall trends have been known since the early work of, for example, Veizer & Compston (1974), Burke et al (1982), Popp et al (1986), Brookins (1988), Kramm & Wedepohl (1991), Nishioka et al (1991) and Denison et al (1994). The results of these pioneering studies were confirmed by data generated from conodonts (e.g.…”

“…Canadian (Sverdrup Basin) and Russian (Moscow Basin) brachiopods of the Late Carboniferous (Bruckschen et al 1999), as well as whole-rock carbonate data from the Carboniferous-Permian transition in the USA (Tierney 2010), suggest a more radiogenic value of 0.7082. Lower values of approximately 0.7080 for this boundary are supported by whole-rock carbonate data of the Akiyoshi Limestone (Nishioka et al 1991), and well-preserved earliest Permian brachiopods from the USA and Russia (Korte et al 2006).…”

“…2), representing the largest sustained downwards trend of the marine 87 Sr/ 86 Sr curve in the Phanerozoic McArthur et al 2012) and this is well documented globally (Burke et al 1982;Nishioka et al 1991;Denison et al 1994;Morante 1996;Korte et al 2006;Tierney 2010). The slope of this downwards trend is not constant through time: relatively steep intervals of the Asselian-Sakmarian and Wordian-Capitanian are separated by a more gentle decrease during the Artinskian-Roadian (Fig.…”

“…This trend starts from a ratio of approximately 0.7083, and reaches approximately 0.7080-0.7082 at the Carboniferous-Permian boundary (298.9 Ma) (Burke et al 1982;Nishioka et al 1991;Denison et al 1994;Bruckschen et al 1999;Korte et al 2006;Tierney 2010). Canadian (Sverdrup Basin) and Russian (Moscow Basin) brachiopods of the Late Carboniferous (Bruckschen et al 1999), as well as whole-rock carbonate data from the Carboniferous-Permian transition in the USA (Tierney 2010), suggest a more radiogenic value of 0.7082.…”

“…DePaolo & Ingram 1985;Palmer & Elderfield 1985;Hodell et al 1989Hodell et al , 1991. For the Carboniferous and Permian, additional work on the marine 87 Sr/ 86 Sr trends was carried out by Popp et al (1986), Brookins (1988), Kramm & Wedepohl (1991) and Nishioka et al (1991), and later reevaluated by Denison et al (1994) and Denison & Koepnick (1995). McArthur (1994) emphasized that excellent sample preservation is crucial for highresolution Sr isotope stratigraphy.…”