Paleoclimate and ecology of Cretaceous continental ecosystems of Japan inferred from the stable oxygen and carbon isotope compositions of vertebrate bioapatite

Abstract

We investigated the environmental conditions that prevailed in continental ecosystems recorded in sedimentary deposits of Japan during the Cretaceous through the analysis of oxygen and carbon isotope compositions of phosphate (δ 18 O p ) and apatite-bound carbonate (δ 18 O c and δ 13 C c ) of vertebrate teeth and bones. Local surface water δ 18 O w values were calculated using known phosphate-water isotope fractionation equations. Anomalously low δ 18 O w values of local waters strongly suggest a significant contribution of high-altitude precipitation from nearby mountains to local surface waters. Mean air temperatures were estimated using a global meteoric water δ 18 O mw value -Mean Annual Air Temperature relationship, and compared to surface water temperatures estimated from fish apatite δ 18 O p values. Local mean annual precipitations (MAP) were estimated using the known relationship existing between MAP and C 3 plant δ 13 C p value, the latter being calculated using apatite-diet 13 C-enrichment applied to plant-eating sauropod and ornithopod dinosaur δ 13 C c values. Reconstructed environmental conditions suggest that climate changed from cool temperate to warm temperate, being relatively cold and dry during the Late Hauterivian and Barremian to warmer and seasonally more humid during the Aptian and Albian, and even warmer during the Cenomanian-Coniacian. Proposed thermal evolution during the Early Cretaceous is compatible with the absence of thermophilic taxa such as crocodylomorphs before the Aptian in the fossil record of Japan.

Relationship among paleosol types, depositional settings, and paleoclimates in Tetori group (Lower Cretaceous, central Japan)

“…Among these, the latitudinal effect, altitudinal effect, and burial diagenesis have provided almost the same effect between the two sections as they belong to the same stratigraphic unit (Section 2). With regard to the altitudinal effect, Amiot et al (2021) suggested that the depositional basin of the Tetori received water influenced by the altitudinal effect and that δ 18 O of the surface water was decreased. If such effects common to both sections caused the 2 ‰–7 ‰ decrease in δ 18 O, the further decrease in δ 18 O in the Section K5 (about 2 ‰–8 ‰; Figure 10) would reflect the remaining two effects, namely, amount effect of precipitation and/or transportation distance of clouds.…”

“…Paleoclimatic reconstructions were mainly conducted from the following proxies: (1) plant fossils (Kimura, 1979;Sakai et al, 2020;Spicer et al, 2002;Yabe et al, 2003), (2) animal fossils (Amiot et al, 2011(Amiot et al, , 2015(Amiot et al, , 2021Owocki et al, 2020), and 3) climateindicative sediments and materials (Hasegawa et al, 2012;Li et al, 2016;Ufnar et al, 2008). Numerical simulations were also conducted (Fluteau et al, 2007;Sewall et al, 2007;Suarez et al, 2011).…”

“…A similar result was also reported by a previous study based on various climate-indicative sediments (e.g., eolian sandstones, red beds, and lacustrine deposits), suggesting that the paleoclimate in the East Asia was humid in the northern part and arid in the southern part by reflecting the shift of a subtropical high-pressure belt toward the equator during the Aptian to Turonian (Hasegawa et al, 2012). Recent studies have conducted a more detailed estimation using oxygen isotopes of vertebrate fossils and carbon isotopes of plant fossils and suggested that East Asia during the Barremian to Albian was separated by natural barriers, such as mountains, into a mosaic climate ranging from hot to cool and from arid to humid (Amiot et al, 2015(Amiot et al, , 2021. A comparable result was also obtained from a study based on numerical simulations (Fluteau et al, 2007).…”

Early Jurassic palaeoclimate in Southwest China and its implications for dinosaur fossil distribution

“…Using the phosphate–water oxygen isotopic fractionation equation established for extant vertebrates, it is possible to estimate the δ 18 O w value of meteoric water from the δ 18 O p value of apatite phosphate. For dinosaurs, the δ 18 O value of meteoric water (δ 18 O w ) could be estimated using the present‐day relationships established between birds, the closest living relatives to dinosaurs, and meteoric water (Equation ; Amiot et al, 2017); this estimation has been recently tested on Cretaceous dinosaurs (Amiot et al, 2020). In this study, the average δ 18 O p value is 18.2 ± 0.1‰.…”

Biodiversity of ecosystems in an arid setting: The late Albian plant communities and associated biota from eastern Iberia

“…Arid environments were inferred for Early Cretaceous floras of Quedlinburg (Germany) and Las Hoyas (Central Spain) based on occurrence of dwarf lycopod Nathorstiana and fern Weichselia [ 21 , 22 ]. Reconstructions of Cretaceous continental ecosystems of Japan based on stable oxygen and carbon isotopes also suggest semi-arid conditions [ 23 ]. In addition, aeolian sandtones provide direct evidence of a desert environment during the mid-Cretaceous in mid- to low latitude Asia [ 24 ].…”