Page 121 - Introduction to Paleobiology and The Fossil Record

108 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Today Warm Cool
Pleistocene
Cool Tropical Cool temperate
Coal
Coal
Bauxite
and Tillites
Wet
Tertiary Laterite
Warm temperate
Kaolinite(and coal and evaporite)
Warm Crocodiles
Palms and mangroves
Arid Cold
Tillite
Dry
Evaporite
Cretaceous Dropstone
Calcrete
Glendonite
Cool
“Paratropical” = high-latitude bauxites
Jurassic
Figure 4.24 Some key indicators of climate and
Warm temperature. (Courtesy of Christopher Scotese.)

Triassic

term climatic fluctuations have been related
Permian to Milankovitch cycles (see p. 36), patterns of
Cool change in climates and sedimentation patterns
Carboniferous that are driven by changes in the eccentricity,
obliquity and precession of the Earth’s orbit
Warm These short-term trends are associated with
Devonian and generally on scales from 20 to 400 kyr.
Silurian evolutionary changes at the speciation level
Cool and more local regional changes in the com-
Ordovician position and structure of ecosystems (Box
4.8).
Warm
Cambrian
Long-term trends

As noted above, the Earth has oscillated
Precambrian between greenhouse and icehouse conditions
Cool (Box 4.9) at least five times in the past 900 myr

(Frakes et al. 1992). These megacycles have
been compared with patterns of change in
22 17 12 extinctions, sea level and volcanicity (Fig.
Average global temperature (°C) 4.26). Moreover, there may be a correlation
between these variables and the assembly and
Figure 4.23 Climate change through time, breakup of the supercontinents. In marine
showing alternations between icehouse and environments two extreme states occurred:
greenhouse worlds. (Courtesy of Christopher
Scotese.)
1 The icehouse state involved unstratifi ed,
unstable oceans, cool surface waters
precipitation and temperature in the recent between 2 and 25°C and bottom waters

past may have influenced the course of human ranging from 1 to 2°C together with
events and almost certainly impacted on the rapidly moving bottom waters, rich in
direction of hominid evolution during the oxygen and with high productivity in
Late Pliocene and Pleistocene. Many short- areas of upwelling.