Info On On Fossil Plants

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101 102 103 Ir abundance (ppt)

10-1 100 101 102 Angiosperm pollen/fern spores

101 102 103 Ir abundance (ppt)

10-1 100 101 102 Angiosperm pollen/fern spores

Figure 5.7 Iridium concentrations (black dots) and ratios of angiosperm pollen to fern spores (triangles) in the York Canyon Core; major deflections mark the K-T boundary (from Orth et al. 1981). Reprinted by permission.

horizon at the outcrop localities (Figure 5.8). Realizing that data points as far apart as New Mexico and Montana were evidence of a continent-wide event, Tschudy made an insightful interpretation about the plant communities that flourished just after the K-T extinction event. He had observed that not only were palynological assemblages of the fern-spore spike overwhelmingly dominated by spores of ferns, but that almost all of the spores were of a single species. This observation conjured up an image of a landscape almost completely covered by a single species of fern, a pioneer species on a terrain laid waste by the extinction event. The first plants to reinhabit the devastated, post-extinction landscape were ferns. Ferns have the ability to regenerate quickly from rhizomes and quickly produce vast numbers of reproductive bodies (spores); and perhaps more importantly, as non-seed plants, they easily reproduce themselves from spores alone.

Tschudy found a modern analogue for this pioneer plant community in descriptions of the volcanic island of Krakatau (Krakatoa), Indonesia, which had been essentially wiped clean of vegetation by a cataclysmic explosion in 1883. Richards (1952) published an account of the recolonization of Krakatau by

Iridium (parts per trillion) 100 1000

Iridium (parts per trillion) 100 1000

Parts Per Trillion Atoms

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