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

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, coastalplain 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 Fades Associations, recording sediment accumulation in I. 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 Fades Association accounts exclusively for the upper 120 m of the measured section. The MSD Fades 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. (C) 2015 Elsevier B.V. All rights reserved.