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Climates Past

Nina Baghai

Interpreting Pre-Quaternary Climate from the Geologic Record. Judith Totman Parrish. 338 pp. Columbia University Press, 1998. $65.

Paleoclimatology is the study of ancient climates that existed before humans began collecting instrumental measurements of weather (rain gauges for precipitation, thermometers for temperature, barometers for sea-level pressure and anemometers for wind direction and speed). Since temperatures, precipitation and atmospheric conditions are not fossilized directly, paleoclimatologists look at natural phenomena that are climate dependent and retain a measure of dependency. Paleoclimate proxies include tree rings, fossil pollen, paleosols, glacial terminus positions, ocean sediments, ice cores and invertebrates.

The study of pre-Quaternary climates has been a growing field since the 1960s with the breakthrough and acceptance of plate tectonics. Many scientific models have been developed, and an enormous amount of data has been collected from the geologic record. Interpreting Pre-Quaternary Climate from the Geologic Record is a valuable sourcebook that describes how various indicators are used to interpret paleoclimate. Parrish compiled and summarized the work of many scientists who have contributed to the reconstruction of pre-Quaternary climates.

The author introduces the subject with useful background on atmospheric changes, paleogeography, time and correlation, and paleoclimatic indicators. She discusses strengths and problems associated with each concept—for example, how temporal climatic patterns, including evaporation and precipitation, are often influenced by local geography. Shoreline positions, the location of continents and altitudes also need to be considered when deducing paleoclimates.

The bulk of this text emphasizes biotic and lithologic paleoclimate indicators associated with marine and terrestrial environments. Microfossils including calcareous nanofossils, dinoflagellates, diatoms, conodonts, radiolarians and macrofossils (trilobites, graptolites, corals and brachiopods) provide information about paleoclimate patterns in marine realms, whereas pollen, nonmarine ostracodes, terrestrial macrofossils and trace fossils yield information regarding terrestrial climates. Parrish provides exceptional tables on angiosperm leaf factors, modern vegetational biomes and wood anatomical characters that possess paleoclimatic significance. She discusses how dispersed plant cuticles provides advantages offered by neither pollen nor plant megafossils. Their thickness, size, morphology of stomata and presence or absence of trichomes can denote whether the climate for a region was arid, humid or temperate.

Parrish also discusses marine, terrestrial and freshwater lithologic indicators. Considerable attention is allocated to coal beds, paleosols, evaporites, glacial deposits, fluvial and alluvial processes and shallow-water carbonates. In one subsection, she mentions how vegetation, tectonics and atmospheric CO2 information that is contained in rocks reveals potential climate. The photosynthetic metabolism of plants (C3, C4 and CAM, crassulacean acid metabolism) is closely tied to the partial pressure of atmospheric CO2 and to climate. Most plants have C3 metabolism, whereas C4 and CAM plants are prolific in arid and dry climates.

A short chapter focuses on climate models and their role in pre-Quaternary paleoclimatic studies. Advantages and limitations of conceptual and numerical atmospheric-circulation, oceanic-circulation and geochemical models are treated. Parrish also discusses how the various types of models are related. Atmospheric-circulation models, for example, regard the oceans as a source for heat and moisture; oceanic-circulation models treat the atmosphere as a source of evaporation, precipitation and kinetic energy through winds and as a sink for heat.

The author ends with a discussion of integrative studies of pre-Quaternary climates. As new methods are developed, the interpretation of paleoclimates is strengthened. Parrish uses the Cretaceous climate on the North Slope of Alaska as an example. Leaf-margin analysis on angiosperms, growth-ring width in fossil logs, dinosaurs and turtles and an understanding of the sediment regime augment each other to estimate cold-month mean temperatures.

This text is an excellent sourcebook for professors, students and researchers who want a basic grasp of pre-Quaternary climates. It is not filled with analytical details and grand summaries of data are avoided. Useful charts, tables and figures are presented through each chapter. Paleontologists, palynologists, sedimentary geologists and biologists will want to consult this book for the wealth of information it contains.—Nina L. Baghai, Biology, Delta State University, Cleveland, Mississippi

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