Constraining the Timing and Amplitude of Early Serpukhovian Glacioeustasy With a Continuous Carbonate Record in Northern Spain

During the Late Paleozoic Ice Age (LPIA, 345–260 Ma), an expansion of ice house conditions at ∼330 Ma caused a nearly synchronous, global unconformity. Subaerially exposed paleotropical carbonates were dissolved by meteoric waters, mixed with the light terrestrial carbon, and recrystallized with overprinted, diagenetic δ¹³C values. In Northern Spain, development of a rapidly subsiding foreland basin kept local sea level relatively high, allowing continuous carbonate deposition to record δ¹³C without meteoric overprint. The Spanish sections show a 2‰ increase in δ¹³C that can be modeled as the ocean's response to the creation of a significant light carbon sink through widespread meteoric diagenesis of marine carbonates during the near-global hiatus. About 15–35 m of sea level fall would have exposed a large enough volume of carbonate to account for the positive excursion in δ¹³C of oceanic DIC. Combining the δ¹³C data with high resolution biostratigraphy and new ID-TIMS U-Pb zircon ages from interbedded tuffs, we calculate that the depositional hiatus and glacioeustatic fall caused by the early Serpukhovian phase of ice growth lasted for approximately 3.5 My.