Marine reptiles and climates of the Jurassic and Cretaceous of Siberia

Abstract

All available data on the Jurassic and Cretaceous climates of Siberia, based on isotope, palaeontological and lithological markers are summarized. Late Pliensbachian cooling, early Toarcian warming, followed by late Toarcian to Middle Jurassic cooling and long-term Late Jurassic warming are well-recognized. Gradual cooling started since the late Ryazanian and continued during the whole Early Cretaceous except the short early Aptian warming event. At the beginning of the Late Cretaceous climate became warmer with warming peak at the Cenomanian–Turonian transition. During the middle and late Turonian climate became colder. During the Coniacian–Campanian time interval climate became warmer, but at the end of the Campanian new cooling event occurred. New records of marine reptiles from the Toarcian, Kimmeridgian, Volgian and Santonian–Campanian of the north of Eastern Siberia are described. All data concerning marine reptile occurrences in the Jurassic and Cretaceous of Siberia are reviewed; these records (from 51 localities) are mostly located at high palaeolatitudes. The analysis has revealed that most of the localities containing fossil reptile remains were llocated in the Transpolar palaeolatitudes (70°–87°). There are no direct relationship between climate oscillations and distribution of these animals. Taking into account recent data arguing that nearly all groups of the Jurassic and Cretaceous big marine reptiles were able to maintain constant body temperature and also were capable make long-range seasonal migrations, any conclusions concerning usage of these animals as markers of warm climate should be treated with a caution.