Carbon isotope stratigraphy of terrestrial organic matter for the Turonian (Upper Cretaceous) in northern Japan: Implications for ocean-atmosphere  13C trends during the mid-Cretaceous climatic optimum

Abstract

Carbon isotope data of terrestrial organic matter (δ 13 C TOM) obtained in Hokkaido, northern Japan, from the marine Cretaceous Yezo Group along the northwestern Pacifi c margin elucidated a detailed chemostratigraphy for the Turonian Stage in this region of East Asia. Chemostratigraphic intra-basin correlation reveals three positive δ 13 C TOM events in the Middle-Upper Turonian of the Yezo Group. δ 13 C TOM fl uctuations in these events show similar patterns in the Yezo Group, indicating that terrestrial organic matter is mixed suffi ciently before deposition in the Yezo Basin. These δ 13 C TOM events are correlated with previously documented δ 13 C carbonate events in Europe (the Lulworth-Round Down, Glynde-Pewsey, and Late Turonian Events) based on global biostratigraphy. Our chemostrati graphic correlations strengthen the use of these δ 13 C events for global correlation of the Turonian marine successions. In addition, global correlation of Turonian marine and terrestrial δ 13 C events identifi es changes in isotopic difference between δ 13 C TOM and δ 13 C carbonate (Δ TOM-carbonate), which are interpreted to refl ect changes in atmospheric pCO 2 levels, and climate-driven stresses of humidity and soil processes. In earlier stages of Turonian, Δ TOM-carbonate values are increased. Elevated atmospheric pCO 2 , and increased humidity and soil processes in enhanced greenhouse conditions during mid-Turonian, are interpreted to enlarge Δ TOM-carbonate values. In later stages of Turonian, Δ TOM-carbonate values are at a constant level, and the lowering of atmospheric pCO 2 or decrease of climate stress related to the diverse paleoclimatic cooling is interpreted to have restored the ocean-atmosphere δ 13 C trends.

Intercontinental correlation of organic carbon and carbonate stable isotope records: evidence of climate and sea‐level change during the Turonian (Cretaceous)

“…The isotopic linkage between marine and terrestrial carbon reservoirs means that carbon isotope stratigraphy is potentially a powerful tool for high‐resolution correlation between marine and non‐marine successions. Extensive work has been undertaken on characterizing δ 13 C trends in bulk terrestrial organic matter in the Turonian Yezo Group of Japan (Hasegawa & Saito, ; Hasegawa, , ; Hasegawa & Hatsugai, ; Hasegawa et al ., ; Tsuchiya et al ., ; Uramoto et al ., , , ; Hayakawa & Hirano, ; Takashima et al ., , ), enabling comparison to marine δ 13 C records.…”

“…Upper Cretaceous marine carbonate has typical δ 13 C carb values of 1 to 3‰ (Wendler, ). By contrast, carbon isotope fractionation during photosynthesis under high p CO 2 conditions has led to Cretaceous marine organic matter exhibiting low δ 13 C org values ranging from −26‰ to −28‰ (Hayes et al ., ; Meyers, ), which are lower than coeval land plant or terrestrial organic carbon, with average δ 13 C org values of −23‰ to −25‰ (Dean et al ., ; Gröcke, ; Hasegawa, ; Uramoto et al ., ).…”

“…Most stratigraphic studies of Cretaceous carbon isotopes have focussed on δ 13 C time series obtained from marine bulk pelagic or hemipelagic carbonates (Scholle & Arthur, ; Jenkyns et al ., ; Weissert et al ., , ; Herrle et al ., ; Katz et al ., ; Sprovieri et al ., , ; Jarvis et al ., , ; Wendler, ). However, a unique feature of carbon isotope chemostratigraphy is the ability to compare records derived from oxidized carbon (carbonate, δ 13 C carb ) and reduced carbon (organic matter, δ 13 C org ) reservoirs (Jarvis et al ., ), and between marine and non‐marine (terrestrial) environments (Gröcke et al ., , ; Uramoto et al ., ).…”

“…The Cenomanian–Turonian boundary (CTB) interval ( ca 94 Ma) is characterized by a large global positive excursion of δ 13 C spanning ca 500 kyr that occurs in marine carbonates (values reaching >5‰ δ 13 C carb ), and both marine and terrestrial organic matter (Schlanger et al ., , ; Arthur et al ., ; Jarvis et al ., ,b, , ; Jenkyns et al ., ; Hasegawa, ; Takashima et al ., ; Uramoto et al ., ; Joo & Sageman, ). This phenomenon is an expression of Oceanic Anoxic Event 2 (OAE2; Schlanger & Jenkyns, ), one of the best developed and geographically most extensive of the Mesozoic OAEs (Jenkyns, ), which represents an episode of widespread ‘black shale’ deposition and a major change in the dynamics of the global carbon cycle.…”

Geochemical and palynological sea-level proxies in hemipelagic sediments: A critical assessment from the Upper Cretaceous of the Czech Republic

“…(2) lower terrestrial nutrient fluxes caused by reduced rates of weathering, low pCO 2 (Hasegawa, 2003;Uramoto et al, 2013) and cooling during the Late Turonian climate event (cf. Voigt, 2000;Voigt and Wiese, 2000;Voigt et al, 2004).…”