U-Pb speleothem geochronology reveals a major 6 Ma uplift phase along the western margin of Dead Sea Transform

Abstract

The timing of vertical motions adjacent to the Dead Sea Transform plate boundary is not yet firmly established. We utilize laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb geochronology of carbonate cave deposits (speleothems) to constrain paleo-groundwater levels along the western margin of the Dead Sea Transform and provide a proxy for the timing of large-scale incision and tectonic uplift. Phreatic speleothems can form in caves that are located slightly below the groundwater level. Tectonic uplift and/or base level subsidence can trigger incision of canyons and induce a drop in the groundwater table. This can cause dewatering of the caves, cessation of the deposition of phreatic speleothems, and initiation of growth of vadose speleothems. The transition between deposition of phreatic and vadose speleothems can therefore reflect tectonic or erosive events. We obtained 102 U-Pb ages from 32 speleothems collected from three cave complexes across a 150-km-long, north-to-south transect. These ages indicate that phreatic deposition began between 14.68 ± 1.33 and 11.34 ± 1.62and ended by 6.21 ± 0.59 Ma. Later, vadose speleothems grew intermittently until the Quaternary. These results suggest an abrupt drop in the water table starting at ca. 6 Ma with no re-submergence of the caves. We interpret this to indicate river incision of ∼150−200 m that was driven by uplift and folding of the western margin of the Dead Sea Transform and by inland morpho-tectonic, base-level subsidence in the Dead Sea area. The observed timing corresponds with a change in the Euler pole of the plates motion along the Dead Sea Transform. The growth period of phreatic speleothems suggests groundwater level stability and limited vertical tectonic motions between 14 Ma and 6 Ma.

Sources, Timing, Environmental and Tectonic Implications of Epigenetic Mineralization Along the Arabian‐African Plate Boundary

“…During mineralization, these sites must have been positioned below the water table to allow deep‐seated brines (i.e., that include a marine and crustal components suggested by previous studies and in Section 5.1) to interact with the host rock, indicating that the mineralization occurred prior to the surface uplift that created the water divide. Constraints on the timing of surface uplift come from recent U‐Pb dating phreatic and vadose cave deposits in the Negev, indicating that the region was below the water table during the mid Miocene, and emerged above the water table at 6.21 ± 0.59 Ma (Chaldekas et al., 2021). These field relationship indicate that epigenetic mineralization occurred in the northern quadrant of the northern Negev in the time‐interval between the deposition of Heimar conglomerate (mid‐Miocene) and the establishment of the current water devide (late Miocene)—but do not preclude previous mineralization event(s) occurring as early as the Campanian (∼72.1 Ma) for deposits hosted in Cretaceous rocks throughout the northern Negev.…”

U‐Pb Geochronology of Paleosol Carbonate Cements by LA‐ICP‐MS: A Proof of Concept and Strategy for Dating the Terrestrial Record

“…Access to a well‐calibrated series of reference carbonate standards (Guillong et al., 2020; Hill et al., 2016; Nuriel et al., 2021; Roberts et al., 2017) and new in‐field and laboratory strategies increases the potential for robust U‐Pb carbonate dating (Guillong et al., 2020; Montano et al., 2021, 2022; Rasbury et al., 2021, 2023; Roberts et al., 2020). The successful application of LA U‐Pb carbonate geochronology to constrain the timing of carbonate precipitation and diagenesis in a given stratigraphic succession or sedimentary basin is now well documented (e.g., Chaldekas et al., 2022; Elisha et al., 2021; Godeau et al., 2018; Gulbranson et al., 2022; Q. Li et al., 2014; Parrish et al., 2018; Rasbury et al., 2021; Rembe et al., 2022; Roberts & Holdsworth, 2022). This body of work opens up opportunities for dating the sedimentary record.…”