A cool time in the Early Jurassic: first continental palaeoclimate estimates from oxygen and hydrogen isotope ratios in chert from Navajo Sandstone carbonate lenses, Utah (USA)

Stable and clumped isotopes in desert carbonate spring and lake deposits reveal palaeohydrology: A case study of the Lower Jurassic Navajo Sandstone, south‐western USA

“…Peterson & Pipiringos, ; Peterson, ). The use of chert‐based palaeotemperature estimates (Kenny, ) and modern geothermal gradients inherently introduces some (generally unquantified) uncertainty in the starting conditions for these calculations. The relative insensitivity of apparent‐equilibrium models at this range of temperatures, however, suggests that even large (±5°C) differences in either starting temperature or geothermal gradient would have a fairly limited impact on burial depth estimates (≤0·5 km).…”

“…The large magnitude of change (>35°C), however, is more likely to be indicative of a secondary, burial-related signal, given that the entire stratigraphic section thickens to the west (Peterson & Pipiringos, 1979;Peterson, 1988;Blakey, 2008). If these carbonate rocks are assumed to have all been precipitated in temperate lacustrine environments around 20°C (Kenny, 2015; estimated from chert), and the geothermal gradient within the Navajo basin was consistently ca 30°C km À1 (e.g. Parry et al, 2009), the approximate burial depth of these sites can be estimated based on apparent-equilibrium modelling of the measured clumped isotope temperatures here (e.g.…”

Early Jurassic climate and atmospheric CO<sub>2</sub> concentration in the Sichuan paleobasin, southwestern China

“…S3a; e.g., Liu et al, 2016;Qian et al, 2016;and this work). In the Newark basin of eastern North America, climate-sensitive sediments such as nodules of carbonate and gypsum (pseudomorph), as well as mudcrack in mudflat facies, indicate an arid climate in the fifth cycle of the Hettangian (> 199 Ma) Passaic Fm (Kent et al, 2017). The more widespread eolian Navajo Sandstone, dated as Hettangian-Sinemurian (200-195 Ma;Parrish et al, 2019), indicates arid in the Colorado Plateau (Fig.…”