Onset of the glacioeustatic signal recording late Palaeozoic Gondwanan ice growth: New data from palaeotropical East Fife, Scotland

• Upper Mississippian strata in eastern Scotland show upward change in cyclothem style.
• Change discloses onset of eustatic signal related to Gondwanan ice growth.
• Initial onset occurred at 332 Ma, main onset at 330.5 Ma.

Estimates as to the timing of initial Gondwanan ice growth during the late Mississippian onset of the late Palaeozoic Ice Age vary among different studies. This raises the question of whether or not the initial ice center growth was globally synchronized. This paper documents a 462 m thick measured vertical section through cyclical, coastal plain and shallow marine strata of late Mississippian age in the palaeotropical realm of eastern Scotland that bears significantly on the question of onset of the glacioeustatic signal associated with major Gondwanan ice growth. The complex succession was resolved into three Facies Associations, recording sediment accumulation in 1. Coastal Alluvial Plain (CAP), 2. Estuarine (EST) and 3. Marine Shelf/Deltaic (MSD) environments of deposition. The lower part of the measured section is dominated by the CAP and EST Facies Associations, with increasing contributions from the MSD Facies Association upward through the succession. The MSD Facies Association accounts exclusively for the upper 120 m of the measured section. The MSD Facies Association preserves evidence for numerous, high-magnitude (minimum 22–40 m) relative sea-level excursions, in contrast to the other two Facies Associations which show evidence for only minimal changes in formative water depth. Occurrences of the MSD Facies Association are interpreted to record a glacioeustatic signal. Initial onset of this glacioeustatic signal is recorded in the central part of the measured section, corresponding to the Asbian/Brigantian boundary at c. 332 Ma. The main onset of the glacioeustatic signal in the upper part of the measured section occurred in the lower Brigantian, at c. 330.5 Ma. These estimates are consistent with those from other studies both of the near-field record and of far-field “cyclothemic” successions of the palaeo-tropics, which indicate a period of progressive palaeoclimatic deterioration into the late Palaeozoic Ice Age during the Asbian and Brigantian stages of the Mississippian.