Greg Retallack's paleopedology group at the University of Oregon
is interested in the effects of major events in the history of life
on the evolution of soils. Such major events include the origin of
life, the advent of life on land, the evolution of land plants, the
first forests, the rise of angiosperms, spread of grasslands, and the
appearance of humans and human cultures. Each of these events had
profound consequences for soils that are recorded within paleosols.
Also of interest is the record of paleoenvironmental change in
paleosols at times of life crisis, such as the Permian-Triassic and
Cretaceous-Tertiary boundaries. Preliminary studies using this
worm's-eye view on each of these topics have been undertaken, and are
summarized in a recent textbook, Soils of the past (1990), now in
preparation for a second edition (anticipated 2001). The overall aim
of this research is to construct a general history of soil and
environmental change on Earth.
Currently funded work involves paleoenvironmental changes revealed by paleosols at the Permian-Triassic boundary in the Transantarctic Mountains of Antarctica, the Countess Range of New Zealand and the Sydney Basin of Australia. The boundary can now be located in both marine and non-marine sequences across the boundary, and shows that the great extinctions in the sea were synchronous with those on land. The Permian-Triassic boundary initiated a paleoclimatic regime of humid cool temperate climate even at high paleolatitudes, in contrast to the marginally frigid climate revealed by Permian coal seams similar to boreal aapamires and palsamires. The boundary also extinguished peat-forming plants, so that the 10 Ma of the Early Triassic is peculiar in lacking coal anywhere in the world (Fig. 1).
Figure 1. Student Evelyn Krull beside a thick, clayey paleosol in early Triassic rocks of the Allan Hills, Antarctica.
This gray and chemically leached paleosol formed in a humid bottom
land environment, yet is not associated with coals. Its degree of
differentiation is comparable to that of soils forming at latitudes
of 50° but its paleolatitude was about 65°. The Early
Triassic was a peculiarly warm and peatless time following the
greatest life crisis in Earth history. More
photographs of research in the field.
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accesses since 18-Jan-96 Last modified 3/9/00