Salt Range Formation of Pakistan Preserves Unique Record of Volcanic Fertilization During the Ediacaran Shuram Excursion

ABSTRACT Thin, discontinuous, organic‐rich oil shale beds in the siliciclastic‐evaporitic Salt Range Formation (SRF) of Pakistan are of approximate Neoproterozoic to Cambrian age based on stratigraphic constraints. The beds are enriched (26–43 wt.% total organic carbon, TOC) in aliphatic organic matter (OM) of low thermal maturity despite their antiquity and position in the foreland fold‐thrust belt of the ongoing compressive Himalayan orogen. We here present a radiometric age constraint—a laser ablation‐inductively coupled‐plasma tandem mass spectrometry (LA‐ICP‐MS/MS) Rb/Sr isochron age of 568 ± 25 Ma (2σ) from volcanogenic biotite and K‐feldspar in SRF oil shale. The isochron age is imprecise but is supported by new carbonate carbon isotopic data from SRF marl showing extremely light δ 13 C values of −10.29 to −10.85‰ Vienna Pee Dee Belemnite (VPDB), linking SRF deposition to volcanic fertilization during the Shuram isotope excursion (~573–562 Ma) and an open connection to the global ocean reservoir.