Evidence for a fungal event, methane-hydrate release and soil erosion at the Permian–Triassic boundary in southern Israel

Abstract

The transition between the Permian and the Triassic systems in Israel is evident only in the subsurface. Two cores, from the Makhtesh Qatan 2 (core 9) and Avedat 1 (core 5) drillholes, in which the Permian–Triassic boundary was found marked by a fungal event, were sampled at close intervals and analysed for palynological, petrographical, mineralogical, chemical, and isotopic properties. Three palynozones were recorded: Lueckisporites virkkia Zone (Late Permian), Fungal Event, and Endosporites papillatus Zone (Early Triassic). The Fungul Event occurs in a narrow interval of ∼1 m and contains almost exclusively fungal remains and recycled woody particles. The two cores consist of laminated sediments, mainly siliciclastic, that were deposited in very shallow to restricted marine environments with a minor presence of evaporites and no bioturbation. Green glauconitic material and framboidal pyrite suggest suboxic conditions even in the shallow waters; reddish brown particles and plant fragments derived from nearby soils, now outcropping on the northeast side of the Dead Sea. These materials, as well as recycled brown glauconitic grains, suggest a drop in sea level and intense erosion before sedimentation, which was apparently continuous. Major and trace element compositions, including rare-earth elements, do not exhibit any particular pattern that might be related to the Fungul Event or to other core intervals. The rare-earth element patterns are basically normal and their concentration correlates with the clay content, reflecting the provenance of the Arabo-Nubian Massif and its sedimentary rims. Iridium results were mostly at the background level, and therefore the two distinct anomalous values are inconclusive. Microspherules, mainly of ∼2 μm size and Al–Si composition, were observed in a few samples in both cores. Their origin could not be determined, though they are considered to be natural. There was no evidence for shocked quartz. δ13Corg excursion exhibits a marked negative shift in both cores, just below the Fungal Event. The lowest values, −37‰ and −42‰, are among the lowest ever recorded near the Permian–Triassic boundary and suggest large-scale release of methane-hydrates.