period, or mixing by bioturbation of some G. menardii group fossils from interglacial
layers
(^) (After McIntyre et al. 1976.)
(^) CLIMAP (Kipp 1976; McIntyre et al. 1976) carried the argument in another
direction. First, they fitted a multiple, second-degree (squares of variables are entered
as variables) regression equation for the relation between some present-era
oceanographic variable (e.g. mean winter temperature) and sediment-surface faunal
data (actually “factor loadings” from the original analysis) as dependent variables.
Second, they used this equation to predict temperatures at 18,000 YBP from faunal
data for that time. Comparison of today’s sea-surface temperature map with the
glacial era paleotemperature map (Fig. 10.20) shows the strong equatorward collapse
of isotherms resulting from glaciation.
Fig. 10.20 (a) Modern August surface-isotherm map for the North Atlantic Ocean. (b)
August surface isotherm map for 18,000 YBP estimated from transfer functions based
on foraminiferan faunal composition.
(^) (After McIntyre et al. 1976.)