New Research Opportunities in the Earth Sciences - New Research Opportunities in the Earth Sciences - page 63

Figure B2.8 Magnitude and duration of Late Ordovician-Early Silurian glaciation based on
carbonate “clumped” isotope paleothermometry (modified from Finnegan et al., 2011). (A)
Hypotheses regarding the duration of the icehouse interval: restricted largely or entirely to the
Hirnantian stage lasting as few as 500,000 years, with a peak in the Hirnantian interval. Both
the beginning and the end of the Hirnantian stage saw a decrease in marine invertebrate
genus diversity. (B) Δ47-derived near-surface ocean temperature trend for the early Katian to
late Aeronian interval. (C)

18 O (VPDB) trend over the same interval. (D) Relative
contributions of temperature and

δ

18 O water to changes in 18 O (Δ 18 O) between successive

δ δ δ

18 O, and color proportion is scaled to the
relative contribution of temperature change (red) and change in the oxygen isotopic
composition of seawater (blue) to Δ

time intervals. Bars are scaled to the magnitude of δ

18 O. (E) 18 O water (VSMOW) trend. Dotted lines indicate

δ δ

18 O water value for an ice-free
world. Various symbols and colors indicate various fossil organisms and locations. SOURCE:
Finnegan et al. (2011).

18 O water value during the Pleistocene LGM (10) and expected

δ δ