The buoyance of continental lithospheres controls the extent of vertical motions they experience in response to sediment loading and unloading, regulating sedimentation and erosion fluxes to and from continental crusts. Over geological timescales, these fluxes affect the global carbon cycle, influencing Earth’s climate and the evolution of life. Yet, the evolution of lithospheric buoyancy through geological history remains poorly understood. Thermal histories of sedimentary basins that evolved on continental lithospheres record sedimentation and erosion cycles that respond to buoyancy changes and thereby approximate the schedule of continental lithosphere stabilization.
Here we use carbonate clumped isotope thermometry to constrain the stabilization schedule of the Neoproterozoic Arabian Nubian Shield (ANS). We collected 39 carbonate samples from Cambrian, Cretaceous, and Eocene units exposed in Eilat Mts., deposited since the Neoproterozoic over several cycles of sedimentation separated by regional unconformities. We identified and drilled specific mineral fabrics (matrix, fossils, cements) resulting in 44 sub-samples containing >93% calcite or dolomite. We then measured their oxygen (δ18O) and carbon (δ13C) isotope compositions, and clumped isotope temperatures (TΔ47). Preliminary results from the Cambrian Timna Fm. show TΔ47 values ranging from ~37-64℃. Using a solid-state reordering model, this range can be translated to possible peak burial temperatures of 64-100℃. Assuming a geothermal gradient of 25℃ km⁻¹ and a surface temperature of 20℃ these results suggest that the Timna Fm. was buried to a maximum depth of ~1.8-3km. Previous thermochronological studies suggest that the overlying Cambrian Shehoret formation was heated to significantly higher temperatures during the Devonian, which may be interpreted as an episode of deep (>6 km) reburial, and a complex stabilization schedule of the ANS. Our results reject this scenario, favoring a simple, early stabilization schedule for the ANS, in which Devonian heating can be viewed as a local hydrothermal event, rather than a regional burial signal.