Abstract
The δ 18 O values of phosphatic microfossils recovered from NW Ireland are used to determine the timing and magnitude of cooling associated with the onset of the Carboniferous glaciation. Microfossil fish δ 18 O apatite demonstrates a +2.4‰ (V-SMOW) shift, which, once corrected for δ 18 O seawater changes owing to evolving ice volumes, equates to an approximate 4.5 °C reduction in equatorial sea surface temperature between the earliest Asbian and the mid-Brigantian (late Visean). Both conodont and microfossil fish δ 18 O apatite indicate stabilization of an ‘icehouse’ climate during the Brigantian and into the Serpukhovian. Substantial late Visean cooling identified herein is in good agreement with global glacioeustatic records. Supplementary material: Further information on the palaeogeography, lithostratigraphy and palaeoenvironments of the sections examined as well as the sample composition and analytical methods of oxygen isotope analyses is available at http://www.geolsoc.org.uk/SUP18511 .
Highlights
The δ18O values of phosphatic microfossils recovered from NW Ireland are used to determine the timing and magnitude of cooling associated with the onset of the Carboniferous glaciation
The predominantly shallow marine succession examined in NW Ireland represents a unique opportunity to examine the onset of the LPIA due to (i) the relatively expanded temporal record preserved, (ii) commonly occurring ichthyolith and conodont elements and (iii) good biostratigraphical control
The results of oxygen isotope analyses on conodont (n = 12) and ichthyolith (n = 36) apatite samples are presented in Fig. 1. δ18Oichthyolith values show an increasing trend from the basal Asbian to the Brigantian, ranging from 15.1 to 19.1‰ (V-SMOW)
Summary
The δ18O values of phosphatic microfossils recovered from NW Ireland are used to determine the timing and magnitude of cooling associated with the onset of the Carboniferous glaciation. The predominantly shallow marine succession examined in NW Ireland represents a unique opportunity to examine the onset of the LPIA due to (i) the relatively expanded temporal record preserved, (ii) commonly occurring ichthyolith and conodont elements and (iii) good biostratigraphical control.
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