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

Abstract

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.